 We had a secret panel of many, many judges out looking at your posters. They may have talked to you, you probably didn't know who they were. And anyway, we've come up with prizes for the top posters presented. And these are poster prizes sponsored by SPIE. So recognizing, outstanding work. Now, I want to make the point, we make it every single year and it absolutely is true it's a very difficult task because there are so many good posters, it's just impossible practically, but we did converge on a set of winners. And to do the honors of presenting the award, I'd like to invite Katharina Spanberg, past president of SPIE to come up and make the presentations and say a few words. Thank you so much. It's always for me a great, great pleasure to see all of you. And this year I know that you have been very eager students, you have been attending everything and you have fulfilled all the prerequisites for being very good students according to what we have heard here. I so much appreciate the possibility to be here, but I even more would like to point out the possibility for you to be here and to build this network. I am quite sure that during all your time as scientists, researchers, teachers, or whatever you will end up, you will remember the time you had here at ICTP. And I am sure that the network that you have been building up here will remain all your professional life. Wherever I go teaching students, meeting young people, I announce the possibility to go to ICTP and to look into the website, try to apply, and if you are successful, as you have all been here, you are accepted for this workshop. The good thing is also that the learned societies, they appreciate you so much. I represent SPIE. As you heard, my name is Katerina Swenberg. I was the president of this learning society during 2011 and was in the presidential chain a lot of years, and that's the reason why I now have the opportunity to be here. SPIE, as I said, is one of the learned societies supporting this school, and with the support also comes some interesting awards. So in my hand here, I have not less than six awards to the very, very brilliant students. And even if you don't get an award, I'm quite sure that your poster was very good because you are all good. When accepted here, you are judged very good. So, but not all of us can win the loiteries. So that's the reason why I only have six, but that's a lot of awards. And I am very, very happy to distribute them. And I will go through this in the reverse order. So I will start from the third prize. And when I ask people to come here, you come up to me and then they want to make a photo. So you stay here and we congratulate each other and I give you some certificate and also some more substantial thing which I have here in an envelope. So the first one I would like to call on the scene is Maya Sundukova. So Maya, if you are here, please come. I think Maya is... I don't have to help you, should we take pictures? Maya is active in Italy. As I understand. But you originate from Russia. Your name really tells us that. So congratulations. Thank you. Okay. Next person in row is Pega Asgari. Congratulations Asgari. So now you wonder if there are only ladies, only females who will get the prize. I am sure not. Okay, next one. Okay, I already see him. So it's a him and he is here. It's Mudo Bayer. Congratulations. I think we should also congratulate him because he's newly married I think. And he comes from Senegal. So he represents Africa. Okay, so the second one for second place is also a male. So all males listen carefully. The name is Swamnildi Gambar Mahayan. Okay. And he comes all the way from India. Okay. Now we come to the first place. And first person I would like to call is Alexandra Falamas. Alexandra represent Romania. And the last one is Angel Sergio Cifuentes Castro. Representing Mexico. All right, thanks very much, Catarina. Congratulations, winners. Congratulations everybody. It was really a delight to go through those posters for all of us. We're gonna move on to another part of the program now. And so that's the ICOICDP Galliano-Donardo Award honoring Galliano-Donardo for many years ran the optics program here at ICDP and passed away in 2007. So to start things out, I'd like to invite the director of ICDP, Professor Fernando Covedo, who you met on Monday to come up and say a few remarks and then he'll introduce Maria Calvo. Good job. Good afternoon to all of you. And it's great to see these activities moving so well and I've heard all the good things about it. And it was good to see also a lot of already known friends that have been here, coming here for several years. And I think it's an honor for ICDP to be hosting this activity for all these years and to have been able to keep it running for say more than 24 years or so. So also I have to confess I never met Professor Donardo and but whatever I've heard from him was only good things. Everybody has such a good memories about him and all the achievements as he's dedication to ICDP and his mission. And then in particular, this activity of the Winter College, the Sosa and then I think he deserves very much recognition and creating this prize in his honor. I think it's one way to recognize all the effort he dedicated to this field, to optics and to the mission of ICDP. So I think we have here several previous winners which I think is very good. I can see Fred is there, Murana and Murad also. Yes, Murad, yes. So it's great that since it's part of the community of ICDP and the Winter College and with all these collaborations with different optics societies. So for us for ICDP as I said, it's a great pleasure to continue doing this and I think well next year will be the 25th anniversary so this will be a great occasion so probably we can have something even more special. So I'm also very thankful to Joe because Professor Tenerdo passed away and we had to have a contact point at ICDP that can continue the tradition and Joe has been a perfect contact point so it's great that he continues also with us. Very good, so now let me call Maria who is here who will be the person introducing the winner of this prize and give us all the details and as you know before I call here, let me just read, this is about the ICO, ICDP, Galiano Tenerdo award is given annually to researchers younger than 40 years of age from a developing country who have made significant contributions to the field of optics and photonics. The recipient receives a certificate of $1,000 in invitation to participate in and deliver a lecture of other ICDP activity relevant to optics and today of course he will be given the lecture. So I will ask Maria to come and introduce the speaker. Thank you very much. Good afternoon everybody. It's really great to see all of you here attending this wonderful college. I think we've got quite amazing time and I'm sure that you will go back with more knowledge, more network, more friendship and ensure more motivation. This is very important. So now we are going to start with the award ceremony of the ICO, ICDP, Galiano Tenerdo award and as Professor Fernando Quevedo was informing, this is an award that was established earlier in 2000 by the ASAN agreement between the International Commission for Optics and the ICDP and it was by the time when Galiano Tenerdo, you are seeing his picture there. Professor Galiano Tenerdo was responsible of the optics, activities and optics programs at the ICDP and allow me to tell you that he was having a great commitment for having this experiment in optics that he considered was one of the best ways for training and for students just to appreciate the importance of optics. So it was starting in 2000 and in 2007 when we delayed Professor Galiano Tenerdo, we wanted to honor him and to remember his legacy and that's the reason why this award now is having the name ICO ICDP, Galiano Tenerdo award. So for the year 2017, let me explain you the chair of this committee is Professor Murad Skal from University of Cartwrights, Tunisia and the members of the committee are formed by Professor Anna Consortini from the University of Florence, Professor Minchodana I love from Eletra, Professor Joni Emela from ICDP and Professor Amadou Bague from University of Chantatoupe in Senegal. So I would like to thank all of you the committee for the work done and luckily we have a very, very good award this year. The award, the 2017 ICO ICDP Galiano Tenerdo award is awarded to Gautam Kumar Samantha and the citation reads, the award recognized Samantha's significant contribution to the field of non-linear optics, lasers and quantum optics, as well as his efforts in popularizing science among school students in India. So congratulations to Gautam Kumar Samantha and now I shall call him to come just to deliver the diploma and Joni Emela please. Or how are we going to proceed now? Let's get started. Okay, let's bring a, where are you? There you are. Okay, let's bring him, give him a warm welcome. I think besides the lecture he's looking forward to, he's looking forward to a couple other things. Ah, can I ask Fernando to come up and Maria to represent ICO, Fernando represent ICDP and we take a nice picture. Okay, that's all. Do you want a chair? Okay, I'll chair. Okay, I just got elected chair. So now we would like to ask our awardee to come up and deliver a lecture on what's been keeping you very busy these years. And also it's wonderful to recognize that somebody not only does outstanding research, but also is very involved in outreach in the schools and is involved in the society in that way. So I think that's a very good model for all of us. I mean included just to get out and get involved, trying to get that next generation coming in. So anyway, we always like to reward that those kind of efforts. First of all, I would like to thank ICO, ICDP, then at the, then at the award committee, chair by Professor Mauread Jagal for selecting me for this prize. I would also like to thank Professor Joe Naimela for inviting me for this conference here today and giving a talk on this, on my work. Special thanks to the organizing team of ICDP, especially Federica, who made my stay and travel such a comfortable one. Even though the topic I'm just attending here, it's not exactly my research topic, but attending these lectures by distinguished proficient here, and the experimental programs basically demonstrated. I really enjoyed a lot, and hopefully I will carry some of the experiments for my outreach activities in future. Okay, as you already know, my name is Gautam Kumar Samanta. Today I'll talk about nonlinear generation and interaction of structure coherent beam radiation. I am from Physical Research Laboratory, Ahmedabad, India. This is the state in western part of India. It's called Gujarat, and this state is famous for Mahatma Gandhi, the father of nation. And Ahmedabad is the biggest city in that state, and we have this Institute Physical Research Laboratory. It's a premier institute in India, where it's today's India Space Research Program, whatever you see, it's sending rockets to Mars or sending 104 rockets at a time. It's basically started from this research institute. And here we have many research programs, basically mostly the fundamental research we do. And I joined this institute in 2010 to start a new program on nonlinear optics. So, and then it took something three years for me to make a functional lab. This is the picture of my laboratory. I named it Fortnick Sciences Laboratory, by inspired by my PhD institute, where I did my PhD institute of Fortnick Sciences in Barcelona. And I named that Fortnick Science Laboratory. And as you all know and agree, success of a group basically depends upon in members. I am lucky to have a bunch of good PhD students and postdocs. Here is Adi and his oppur. Both of them has left the group for a postdoc position abroad. But some of you might have seen them last year in this winter college. And he got also a poster award. And some of you might also confuse me with this man who has a lot of similarity with me. And Jabir is a third year PhD student. Oppur Varun is second year. He is a permanent stop on Edwin. And I have a recent postdoc in my group, Srinivas and an M.Tech student. I'm also lucky to continue my collaboration with my former supervisor, Prof. Majid Ibrahim Jade from Institute of Fortnick Sciences Barcelona. And my good friend, Chaitanya, from the same institute. So I have been working on some of these topics here. It's a list of non-linear parametric processes, optical parametric oscillators in continuous or even ultra-first time regime. Basically, these are the two topics what I used to do during my PhD. And I'm still continuing on that one. However, I have started new programs, new projects. It's a structure beam, optical beams, and they are non-linear interaction, structure beam optical parametric oscillators, development of bright entangled photon sources for the quantum optics experiments, and generation of hybrid entanglement and control of special structure of entangled photons. And that is important for some of the quantum optics experiments. And then I'm just starting this new project. It's a generation of Terrahach and few cycle pulse structure beam sources in infrared radiation. So I'm just having the leisure now and I have to start on this one. However, in this today's talk, I'll be basically explaining some of the results we got in last three years from this laboratory. It's structure beam optical, structure optical beams, and then they are non-linear interaction and the structure beam optical parametric oscillators. So before going to the research topic, I want to explain something about my extra curriculum activity, what I do. And I'm passionate to do that one and it was also cited in my award introduction. So when I was doing PhD, that time I used to think why government is spending so much money of taxpayers' money for my research, what I am really passionate of. And sometimes the research what I'm just doing might or might not have direct impact or benefit to the society. And then I thought, okay, let's, if we can just enhance the quality of the human resources by explaining some of the science to the society, that will perhaps, you know, just justify some part of the expenses we are, perhaps this research will have impact in longer time. That's why I was also involved in this Outreach Activity, Outreach Activity during my PhD tenure in ICFO. That's a nice place to start new activities. And then joining a physical research laboratory, I started a hands-on experiment for the students. So I don't know, I have just lost the slide. Okay, so what do we do? We demonstrate some of these basic optics experiments what we see in daily life and through hands-on experiments. So far we have demonstrated or developed 50 experiments, not only concentrating on optics, but also for physics experiments. And some of the equipment also we have built that we carry to the students. So that experiments set up will be optical tweezers. So using some of the optical components for my lab, just build a optical tweezers where we can just trap micron-sized particles and then we demonstrate to the students. And also we have some other thing. So this is basically for the school children explaining some of these basic optics and then when we sit in the interview panels for the PhD students in my institute, I see most of the brilliant students want to do theoretical research. So that's really surprising. And then if you look back, if I look back, then I see the curriculum doesn't really in India but we have that doesn't really support for the experimental research. Wow, how? So we are supposed to do some of these experiments within that curriculum. And the experiments are, most of the cases, the equipment will not work. There will be no professor to explain the physics behind that. And most dangerously, your senior's lab book will be available in the corner and you can go and copy it. So to get marks, you have to complete. So you copy it and you get marks, pass and go to the next course, next semester and then continue. So as a result of this, we don't build the affection to the experiment. So then when we come to experimental research where most of the cases, there is no basic equipment. You have to build most of the cases. That means if you see the kind of research we do during PhD or postdoc or later on and the kind of training we get during the college, there is a big gap. So we tried to make a bridge between these two gaps and to take this concept to the undergraduate student. So we started a program called Physics, Training, and Talent Search. And that started, we started in 2006. It's this year, 2015 we started. And 2016 also we had that one. So we are just having every year in December, we have 15 days residential course where we select 50 students from different colleges in India. And with these two theory courses, one experimental course and I am involved in that experimental part. And for the experiment, so first day we allow the students to go to the lab and lab is empty. There is nothing. And then we ask them some questions, one line or two line questions, like design an experiment to measure the salt's concentration or sugar concentration. Or does interference, some of these questions are there. There are many other questions also for other mechanics problems. And they are given this problem and asked to design the experiment. So initially they will go back, they will study, they will come back, propose in front of us, and then we will just verify whether it's possible or not. And they have to do the experiment. And interestingly, the equipment has to be within the budget of $5. So that is adding some more difficulties and just forcing them to think about the experiment. Initially, the students will not really appreciate. They will think that I am the villain, because whatever they propose, I will be just rejecting that. But at the end, they will really appreciate. And they will tell, OK, we have learned something. And without, so for the experiments, experimental research, not only you need that experiment, at the same time you use your brain to justify some other things. So that's what we do. At the same time, we promote also this, for the career development of our PhD students. So we started last year a conference. It's a student's conference on optics and photonics, where the theme of this conference is organized by student, participated by student. So we have some distinguished lecturer from abroad, sponsored by OSSA. And some Indian young faculties, those who will be just giving a few talks, are mostly it's by the students, given the students. So you can just see this is the picture. And my supervisor was last time as the giving a planetary talk. So in this way, we just promote. And in this conference, I have very little role. I just guide, and I arrange the money for this entire process. So with this, these are some of the activities what I do. But I'll tell about the science part what I do. But in my institute, I am famous for not for the science. I'm famous for the sports, because I love all kind of sports, and I do a lot of sports. So I represent my institute also in some of these tournaments, playing table tennis or tennis. I also play football. However, if I take time, then I go to the lab and do some research. So that's what I'm just going to present today. So here, this is a, in fact, after this hour when it was announced in my institute, then people started wondering, oh, you do also research. Then I say, yes. So this is the content of my talk. I'll talk about the basics of optical vortex. Some of the lectures we have already, some of the speakers already mentioned about the optical vortices. And then generation of optical vortex beams, perfect optical vortex beam and hollow Gaussian beam. And then I'll talk about the control transfer of OEM in an optical parametric oscillator. And a special kind of beam is called airy beam. And I have just shown you some of the results on airy beam optical parametric oscillators and then conclude. So like Gaussian beam, most of the cases, all this nonlinear interaction we study using Gaussian beam. So the Gaussian beam is having intensity distribution, maximum at the center, and falls according to the Gaussian formula. And the phase we'll be having, you can just control that phase, it's a plane or a spherical wave front, you can just make out of it. However, if you just change the spatial structure of the beam by some means, then the beam will carry a spiral phase variation. So with the propagation, the phase of the beam will vary in spiral. So if you take a snapshot anywhere and find out its phase, then there will be a phase variation from zero to two pi or something else. And if you take the intensity plot of that beam, it will show you a donut set intensity distribution where the no light at the center and light at the outer ring. So if you have this phase variation from zero to two pi, then the order is one. It's a vortex, these beams are characterized by their order or topological charge because this topological is being changed. And if you just have this phase variation, zero to four pi or zero to six pi, then this beam will have order two or three and so on. Interestingly, these beams is having optical vortex beam carries orbital angular momentum of image cross for photon. So once this orbital angular momentum associated with this beam was invented after that lot of very different, many different fields has started using this beam like in case of trapping, twizzing and quantum optics it's heavily used because you can just use this degree of freedom orbital angular momentum for hybrid entanglement and so on. In nature also we see such kind of structures like if you have a whirlpool where you can see this water whirls are across this vortex point, it's a singular point or it's a for black hole, tornado and galaxy also. So these are the some nature in nature we can see some of these vortices. In lab one can generate this vortex beam. So holographic technique you make a fork pattern of this and pass this Gaussian beam through it then that will give you a vortex beam. And that for confirmation like the holography we can just interfere this beam with a reference beam the same beam then you can just see that interference pattern depending upon the phase of this reference beam you can have a fork pattern or a spiral phase pattern. Additionally we can also generate this optical vortices taking a Gaussian beam and passing through a spiral phase plate. The phase plate is having thickness variation in transverse plane. So you can have the phase variation in this and if the light passes through that one this phase variation will be imprinted on that beam. So which will in turn result in an optical vortex beam like this, it's a donut shape beam. And you can have different spiral phase plates it's just an order two, three, four but it's very expensive and then technologically you cannot really just go beyond that order four or so and there are only one company which can generate this one for higher power operation. So if you have a vortex beam of power P and order M then the electric field is presented like this one. This is a constant term and you can see here it's a R to the power M, it's a Gaussian part and the spiral phase term here. So from here if you just plot that intensity then you can see here it's R to the power two M because R to the power some parameter is there and as M goes we can have that intensity pattern or dark core size of that beam increasing. So you will have a increasing dark core size of the vortex. So using this beam we started generating optical vortex vortices or perfect vortices and these are the results we have just recently demonstrated. So what do we have done? We have just generated and we have just studied the nonlinear interaction of this beam. So we have just make optical vortices of order one, three, six just for an example. These are the intensity pattern of fundamental beam at one zero six four and which is confirmed through the interference as I showed previously and then we generated a green beam at five 32 and recorded that intensity pattern you can see that intensity pattern is also having that do not say. So which is also confirmed through a new technique it's a tilted lens technique where if you pass this beam through a tilted lens due to the astigmatism in the lens, this beam will split it into characteristics lobes. So counting the number of lobes and reducing by one you can tell what is the order of that vortex. So if you have three number of lobes then it will be order two. You have 13 number of lobes it's order 12. So these processes all they satisfy three conservation law. It's like all nonlinear processes it's energy conservation and momentum conservation that we know. However in this case we realize that orbital angular momentum conservation is also there. So the orbital angular momentum of the input beam is equal to the orbital angular momentum of the output beam. So since it's a second harmonic generation two photons of this is converted into one photon. The OEM of these two photons will add it up to give you a two. So like that so we can see this is a orbital angular momentum conservation. However if you just measure the conversion efficiency of this beam then you see we can see that conversion efficiency is decreasing with the order. And if you go for higher order then it's not really an appreciable intensity useful for some of these applications or many of the applications. So that means with increasing order the conversion efficiency of the beam goes down and then why it's so. If you take the area of this beam with the order then we see that area of the beam is increasing. And since nonlinear interaction is a intensity dependent phenomena you can expect that one by F decrease. Because this area is increasing linearly so we'll have this exponential decay or one by area decay. But orbital angular momentum is also increasing with the increase in order. So we cannot really certainly say whether this decrease in this one has orbital angular momentum has any role in the decrease in this power or not. So for that we generated a new kind of beam it's called perfect vortex beam. So where the size of the beam doesn't change in the OEM or order. So you can see it's a normal vortices it's a increasing order the size is increasing and this is a perfect vortex. So where you can see the size remains unchanged even the order is increasing which is confirmed with this tilted lens technique. And then we did this experiment we take a fiber laser and then made that vortex in the pump and made the perfect vortex through axicon and Fourier transformation at the center of the crystal and generated the green beam. So you see these convert beams and confirm their order. And when we measure the conversion efficiency of these beams with order we can see the conversion efficiency remains almost constant even the order is increasing and a single bus conversion efficiency is 25%. It's a huge conversion efficiency for the structure beam. Normally Gaussian beam is having highest non-linear conversion efficiency and this is the first report where a structure beam is showing highest conversion efficiency of 25% in a single fast configuration. And these are the power scaling thing. So far in all these experiments I just explained let's say you have two photons adding and their OEM is adding because we are just having frequency of conversion. So we are just adding photons going to the lower wavelength and OEM is also added. So is it possible? Let's say we make some scheme where we annihilate or subtract the OEM of these beams. So this is the pictorial representation of the scheme what I am just saying. We take a optical vortex of order L in it's a rotating in clockwise and we take another one in minus sign it's rotating in anti-clockwise direction. So if you just interact these two beams in a non-linear crystal, then what it should be? Basically optical vortex is having a spiral winding. So if you just unwind it, then one can expect that it will be a Gaussian beam. That is a common understanding people maintain because you start with a Gaussian beam, imprint that spiral phase, you get a vortex. So you remove that spiral phase, you should get a vortex Gaussian beam. That is what I say. Some reports are there, but here we show that one. We see some new beam where that intensity distribution of that beam is donut shape, but it's not having orbital angular momentum associated with it. It's called hollow Gaussian beam and that phase distribution of that beam is plain. So we did that experimentally. We started with a fiber laser again and then frequency double into green and then taking that green, we converted it into vortex of different orders using the spiral phase plates and we took that undepleted beam and made also into a vortex and took these two beam, did some frequency mixing in this crystal and generated UV radiation. As you can see, the size of these beams is having intensive distribution like this one and the size is increasing and that is these experimental results and theoretically we saw that one. It's matching with that experiment with theories also matching. So this is the interesting experiment. So all these processes is a frequency of conversion. We are just adding or subtracting. However, in parametric process, when you can just go for the down conversion, you can split one photon into two. So if you start with an OEM, can you just split that OEM among this interacting beam? That is what we thought that will be interesting. Then we will have a certain advantage on that one. So I'm just going to this topic. It's a control transfer of OEM or pump beam among the interacting beam in a parametric oscillator. So in case of parametric process, when you have a pump photon that goes first through the nonlinear crystal due to this nonlinear interaction of that beam that converts into two photons of lower energy, is one of them is historically called signal which is having higher wavelength and another one is called idler. And these processes basically follows all three conservation law. You say energy conservation. So you can just split that energies in anything you can adjust as long as you have this conservation law. The energy of pump is equals to the energy of these two photons. Then you have to also for efficient conversion, you should have a momentum conservation. All this momentum of this beam should match so that you can just transport that energy from the pump to the generated photons. And as we explained previously, the OEM conservation, that means OEM of the pump has to be equal to the OEM of this beam. And if you put this process in a cavity, then it becomes an optical parametric oscillator. It's a single pass and then you can just put that on the oscillator cavity, you make it the optical parametric oscillator. So now the question is, since OEM cannot be divisible, so if you start with an OEM in the pump beam and try to find out, check that what is the OEM of this generated beam. And you can see, we start with the vortex of order one, then we can have two conditions. Condition one, idler can get a Gaussian beam, no OEM, and signal get a vortex beam. Or the idler get the vortex, signal doesn't. So these two processes are equally possible, but is there any favor or does the system favor one of these processes or they support both the processes? So for that, we did the experiment, did this experiment in an OPO. We started, this result is recently accepted in Optica and it will come in the next issue. So we start with a fiber laser, frequency double into green, and took that beam, converted into vortex, and pump that OPO, which is designed in this, it's a two curve mirror and plane mirrors, and we divided that signal and idler into two different arms so that we can individually control these two beams. And when we are having this, and then we monitor the signal and idler along with the pump. So when we have a pump beam in Gaussian intensity distribution, as you can see, which is line intensity, interference pattern is also showing line, there is no phase singularity, idler and signal is also having the same intensity distribution or means it's a Gaussian. However, if you take that input beam as a vortex of order one, then in that case, we get signal as a vortex, idler is Gaussian. That's very interesting. And why it is happening so, that is a question that's stuck. Why the pump is only transferred to the signal, not to the idler one? So for that, we started solving the dynamical equations. These are the formulas, it's nicely written in this paper. And I don't want to go into the details, perhaps you will board with that. So I go to this two conclusions, this condition one, where pump OM is transferred to the signal and idler is having a Gaussian. So in that case, we calculate the threshold condition, you get this formula and do the other way, pump transferred to the idler signal is in Gaussian. So we find out that threshold condition. So if you compare these two conditions, you can see all the parameters are same except these parameters. These are the losses for the signal and the idler. So if the signal loss is high, then this threshold will start and vice versa. So we can conclude here, if the signal loss is more than the idler, the vortex will be transferred to the idler and signal gets that Gaussian beam. If the loss for the signal is low compared to the idler, then we get that vortex transferred to the signal. So that is what theoretically we found. Then experimentally we study. So we measure the transmission of these mirrors and we found that for this red line is losses for the transmission for the idler and this one is the signal. So as you can see here, it's clearly the loss for the signal is lower than the idler. So in that case, when we are pumping with the vortex, we see the signal is always a vortex, idler is always Gaussian. So that means we are just favoring the transfer always to the signal. However, if we just change the loss of this signal using an output coupler, then we can see the signal which was the vortex, now it's giving a Gaussian beam and idler is getting a vortex. That means you can just control the loss of the system and you can transfer selectively which of these beams can take the OM, you have that control. And another important thing is also, let's say you can see we are generating vortex beam from 960 nanometer to 200 nanometer. It's a wide durability, no system is there that can produce over such a long spectral range with higher power. So basically we are incorporating the advantages of optical parametric oscillator to generate a new structure beam, not new, it's a structure beam instead of the Gaussian beam. So normally people work with the Gaussian beam, I'm just trying to do that one of the vortex. And here we have this when you are pumping with one, you can have one plus zero or zero plus one, two cases. So that is what I show. What will happen if you have two? So that's the case. So two can be written two plus zero, zero plus two, one plus one. So three conditions you can just find. So in that case, when you are pumping with order two, then you can see the signal and idler, both of them are getting vertices. Both of them have optical vertices of order one. And if we just reduce the signal loss as compared to idler, then we see signal is having order two and idler is zero and that is confirmed. So we couldn't really just realize the other case because these opiates are continuous wave opiates. And those who have worked in this work with opiates, they might appreciate that it's very difficult to align when you are just incorporating some losses. And for this experiment, it took more than six months for my student to realize. And so if I can just summarize this particular experiment, I can have a table like this. So I have a control parameter with me and I can just transfer this input OM into the signal idler generating an output state. And if I can just modulate this loss very fast, then I can get a modulation in the output state. So that is useful for OM communication. So communication, in case of communication, one can use this rapid switching of OM modes. So that is, so I have just explained some of this thing. In case you are interested, you can just can stay tuned for this paper to come. So with this, I'll just explain all the optical vertices. So I'll just go to the last topic of my talk. It's air beam optical parametric oscillators. This beam is having some fascinating features and I'll explain. So normally when we talk about a laser beam, you can see it's a, in near field, that intensity distribution is a beam size is small and then in the far field the beam will diverge according to the divergence of the beam. However, most of us those who are working here, they will be very happy if I have a beam like this. So the beam doesn't really diverge. So you stay there as it is. This feature is called non-refraction, means beam maintaining its constant size over the propagation distance. It will be also interesting, if you have a feature like this, the beam bends away. So if you have an obstacle, the beam bends away and avoid that obstacle. So it's called self-acceleration or propagation in curve trajectory. And additionally, on top of these two features, if you have another feature, let's say you abstract some part of the beam, but the beam reappears itself. So it heals itself, like biological cell, it heals. It's a reappearance of the structure, we call it self-healing. So if you have all these features, that will be interesting for many applications. And unfortunately the standard Gaussian beam doesn't have, doesn't do not have all these properties. And these features are widely used. Somehow these fascinating experiments, like you generate curve plasma channel or in micro-particle manipulation, you can just sort depending on the size of the beam. It can be, size of the particle, it can be sorted in different ports. And also people use this kind of beam for let's say light-seat microscope. And interestingly, the self-healing property, self-healing property of the beam helps to see the, can look deeper into the human tissues. So that is what these are the features. And this beam was first demonstrated in 2007. When people saw that one, the airy beam, if you take a Fourier transform of airy beam, that gives you a phase variation of cubic phase variation. Okay, this is the cubic phase variation. However, these beams are infinitely extended and in laboratory you cannot do. So for that, you have to put some exponential decay function to accommodate in your laboratory equipment, size of the equipment. So if you have a truncation parameter, still that beam, so if A is equal to zero, it's an ideal airy beam, maintaining all the features over infinite distance. However, if you truncate that beam with some exponential decay function, then still these beams can maintain its properties over a limited distance. So if you take that interference pattern of that beam, it looks like this, and phase profile of this beam is like this one. So typically, if you make this kind of diffraction grating of cubic phase variation, and you eliminate that with a Gaussian beam and do the Fourier transformation, then that will give you an airy beam. It's a two-dimensional airy beam or it's just a one-dimensional airy beam. So we try to use these airy beams because it's having interesting features. And then we try to add whether we can add all the benefits of OPO within that beam. So for that, we have just started this. So this is a pictorial representation of that scheme, which has earned us also a post-deadline paper in 2005, Cleo post-deadline paper, and some of this recent paper in scientific reports. So the scheme is something like this. We have an OPO, it's a continuous wave, and femtosecond anything you want. And you just put a diffracting optical element. So you're just putting a diffracting optical element inside an OPO. That is really challenging until and unless you have proper understanding about the loss mechanism inside the cavity, and especially for the continuous wave regime. So we put a spiral cubic phase mask here, and then in the first diffracted order, we'll have a cubic phase modulated Gaussian beam. And if you take that Fourier transformation of that, it will give you an airy beam. So then once we generated that beam, we try to study whether that characteristic features are maintained or not. So here, this plot is showing the beam. So we recorded that beam intensity profile at Fourier plane with z equals to zero. And then we let that beam to propagate over distance with different z values. As you can see, the beam is curving either. So if you cannot really appreciate that one, then you can perhaps see this one. So we start with the airy beam and the Gaussian beam as a reference. And as you can see, the beam remains, the center of this beam remains, Gaussian beam remains unchanged, whereas it's becoming diverging because of its nature. Whereas this beam started from some point and it's moving across this point, cross section of this x and y plane. So you are just seeing that propagation of that beam along this line. So it's curving away from its electric linear propagation. Then we also measure its line profile. So we just measure the line profile of this beam over the propagation distance. As you can see here, the size of the beam remains unchanged. Even you have just propagate over two meter distance. So over two meter, the beam is perfectly maintaining its features. Then we also studied its cell-willing property. And we just block the beam, central lobe of that beam here. So we have blocked at a Fourier plane and we let that beam to allow, allow that beam to propagate. And as you can see here that after 40 centimeter propagation, that beam, some of the intensities are coming here and here and then it has a full healing. So it's returning, it's coming back to its original shape. And this below one is a theoretical image. It's also supported by the experimental one. So with this, I just come to the conclusion and for the best interest of time, I'll not read all these conclusions. And I hope I have just convinced you that this structure beam is, we can just produce from non-linear interactions and optical parametric oscillators. With this, thank you very much for your attention. I just turned off the microphone. Yeah, you can use this. Okay. I'll use this one over here, this works. Well, thank you very much. It was a very delightful talk. I'm also glad you mentioned at the beginning of your talk some of the outreach things you're doing. And it was a really interesting, I noticed that the director of ICTV was taking note about that $5 experience. Joe. No, that's really very exciting. And then we are just continuing it. No, that's actually really interesting. Is this working? Oh, now it's working. Okay. So the talk is open for questions. While they're thinking about a question, so we, oh, we have a question. Ah, okay. So can you back convert the IRB beam to a Gaussian beam? No, once this beam is, you know, you fabricate it, it cannot be a, because you just lose some of this. So if you can transport it like this and then back convert it. I just forgot to mention that one. So this beam will have some shape with propagation. Since it's a truncated air beam, this features will be over a particular distance. After that, that beam will be a Gaussian beam. So in far field, so if you allow that propagating over long distance, not the ideal one, so truncated one, the one we do in experiment. So in far field, there are some reports, and we also observe. So you just propagate for five meters. You will see that entire beam is collapsing to a Gaussian intensitation, let's say one patch. Yeah, you can. Okay. These are non-defracting beams. Now, is this very similar to what was called a number of years ago, Bessel beams? No, this one, Bessel beam is a different one. It's a, you can just make that Bessel beam with a center one with high density and then it's having rings. But this one is a different one, so it's having different structure. It's just having airy, airy, airy beam. It's a, I think in, I think Berry demonstrated that one in quantum mechanics, that airy function, and airy, airy, airy way packets, which is having all these features. And in optics, because this Hamilton, sorry, Helmholtz equation is having similarity, that's why people started doing the same thing for optics. In 2007, this is the first time anybody has reported for generation, yeah. Maybe I am wrong. I understood that you change the beam to a phase filter. So there are many techniques. You can just imprint that phase. Because the beam propagation is basically, you can just consider that these beams are interfering with each other while propagating, that propagation. So if you just, in case of Gaussian beam, all of them are having the same phase, so they maintain their Gaussian safe distribution and then no different. But if you just imprint some phase in different points of that beam, then they will no longer be Gaussian. So because that interference pattern will change. That is what we do. Either by a holographic technique, so you just say fork pattern, so that phase variation is there in the transverse plane of the beam. Or you have a spiral phase plane, which is having a thickness variation in the transverse plane. So different part of that beam, Gaussian beam, is seeing different phase. So they generate a new structure. It's a completely different structure. Now, by computer, you can just, SLM or the special light modulators are there. You can just put that phase structure in that one. But this spiral, this special light modulators are low intensity devices. So it can handle only 10 milliwatts or 20 milliwatts. I'm just talking about this nonlinear interaction, where you need to handle, let's say, 40 watts, 50 watts, or four watts in that range, because it's a pulse or CW. So in that case, this SLM will not work, especially. So we have to go for this spiral phase plate, which has higher demonstration because it's made of a glass and they cut it into different shapes with a thickness variation, precise thickness variation. And there is one company in Israel who is expert for this one and that they make, and then fortunately, we get that one also from them to do these experiments. Another question. Okay, this is how I do my exercise. Thank you. So when you use two helical beams with the same value of the topological charge but opposite signs through nonlinear medium, you obtain hollow Gaussian beam. Yeah, yeah. So that's dark core. Does it remain dark in the near and far field or during the long propagation difference? If you just, in the near field, it will be always mentoring that one. Some people said that one, it will be a Gaussian beam, but normally that beam doesn't really bring its intensity back to the center. But if you focus that beam, do the Fourier transform, just bringing that far field to the focal plane, then you can see these beams, the Fourier transform of this beam will give you a Lagrory polynomial with radial index, not azimuthal index. So you will see a bright spot with circular rings. So that is what we can maximum get. Means you cannot really get back to the Gaussian. It will maintain its shape over propagation. Yeah. In fact, we have another experiment where we use this hollow Gaussian beam and study the frequency doubling property of that beam. And then if we allow that beam to propagate, the frequency double beam is also hollow Gaussian beam and it maintains its spatial shape over the distance, propagation distance. Yeah. Okay. Congratulations for a nice talk. Just for curiosity, you said that you could use several years to build your lab. Yes. And can you give us an idea of the cost of equipment to see if it can be done in other countries and developing countries? Okay. Roughly. For my experimental one, I should be honest, okay? So I was very lucky because this institute falls under the Department of Space. So Department of Space, this Indian Space Research Organization is coming under the same. And we are also the part of that Department of Space. And according to the budget we have, we have annually we project some budget. That budget is lower than the cleaning budget of all other institutes, okay? So that's why when we ask, I need this. They say, okay, please. You don't need to present. Take that money and go. So, and when I joined, I got a huge amount of money, fortunately, and then started. So it's a, I don't know how much it will be in dollars or euros, but I can tell that one in Indian currency, some Indian currency because it's in crores or, I think it's a few hundred thousand euros or more. So I think it's a two, three millions of that. My own experimental group is having that kind of budget. Yeah. Any other questions? I think the advice is join a space institute. Well, don't go anywhere. I've got a couple of very important announcements, but let's thank our award winner, Dr. Samantha, for the wonderful time. Congratulations.