Professor Sukhdev Roy received the B.Sc. (Hons.) Physics from Delhi Univ. in 1986, M.Sc. Physics from DEI, in 1988, and PhD. from IIT Delhi in 1993. He joined the Dayalbagh Educational Institute in 1993, where he is at present a Professor in the Department of Physics and Computer Science. He has been a Visiting Professor at many universities that include, Harvard, Waterloo, Würzburg, Regensburg, Osaka, City University, Queen Mary University of London, TIFR, Mumbai and IISc. Bangalore and Associate of ICTP, Trieste. He is a Member of the Global Panel of MIT Technology Review.
Prof. Roy has made significant contributions in Photonics that encompass nano-bio-photonics, silicon and neuro photonics, fiber optics, and optical computing.
He is the recipient of AICTE Career Award for Young Teachers, JSPS Invitation Fellowship, Japan, H.C. Shah Research Endowment Prize by Sardar Patel University, 1st IETE B.B. Sen Memorial Award, IETE-Conference on Emerging Optoelectronic Technologies Award, IETE-M. Rathore Memorial Award, the National Systems Gold Medal, and the Distinguished Alumni Award by the Dayalbagh Educational Institute.
He chaired the 8th World Conf. on Nanoscience and Nanotechnology, Philadelphia, USA, 2020. He has delivered more than 100 invited talks in India and abroad that include the International Year of Light commemorative Keynote Address, at the 38th Convocation of the International Council of Academies of Engineering and Technological Sciences (CAETS), in 2015 and at the Annual Meeting of APS in 2008.
He was the Guest Editor of the March 2011 Special Issue of IET Circuits, Devices and Systems on Optical Computing. He is an Associate Editor of IEEE Access, Senior Member IEEE, Fellow of Indian National Academy of Engineering, National Academy of Sciences(India), IETE(India), and Optical Society of India. He is listed in Top 2% in World Ranking of Scientists-2020, in Optoelectronics and Photonics.
https://orcid.org/0000-0001-5682-252X
Publications (9)
This will count as one of your downloads.
You will have access to both the presentation and article (if available).
A detailed theoretical analysis and optimization of high-fidelity, high-frequency firing of the red-shifted very-fast-Chrimson (vf-Chrimson) expressing neurons is presented. A four-state model for vf-Chrimson photocycle has been formulated and incorporated in Hodgkin–Huxley and Wang–Buzsaki spiking neuron circuit models. The effect of various parameters that include irradiance, pulse width, frequency, expression level, and membrane capacitance has been studied in detail. Theoretical simulations are in excellent agreement with recently reported experimental results. The analysis and optimization bring out additional interesting features. A minimal pulse width of 1.7 ms at 23 mW / mm2 induces a peak photocurrent of 1250 pA. Optimal irradiance (0.1 mW / mm2) and pulse width (50 μs) to trigger action potential have been determined. At frequencies beyond 200 Hz, higher values of expression level and irradiance result in spike failure. Singlet and doublet spiking fidelity can be maintained up to 400 and 150 Hz, respectively. The combination of expression level and membrane capacitance is a crucial factor to achieve high-frequency firing above 500 Hz. Its optimization enables 100% spike probability of up to 1 kHz. The study is useful in designing new high-frequency optogenetic neural spiking experiments with desired spatiotemporal resolution, by providing insights into the temporal spike coding, plasticity, and curing neurodegenerative diseases.
A detailed theoretical analysis of low-power, fast optogenetic control of firing of Chronos-expressing neurons has been presented. A three-state model for the Chronos photocycle has been formulated and incorporated in a fast-spiking interneuron circuit model. The effect of excitation wavelength, pulse irradiance, pulse width, and pulse frequency has been studied in detail and compared with ChR2. Theoretical simulations are in excellent agreement with recently reported experimental results and bring out additional interesting features. At very low irradiances (0.005 mW / mm2), the plateau current in Chronos exhibits a maximum. At 0.05 mW / mm2, the plateau current is 2 orders of magnitude smaller and saturates at longer pulse widths (∼700 ms) compared to ChR2 (∼350 ms). Ipeak in Chronos saturates at much shorter pulse widths (1775 pA at 1.5 ms and 5 mW / mm2) than in ChR2. Spiking fidelity is also higher at lower irradiances and longer pulse widths compared to ChR2. Chronos exhibits an average maximal driven rate of over 200 spikes / s in response to 100 pulses / s stimuli, each of 1-ms pulse-width, in the intensity range 0 to 200 mW / mm2. The analysis is important to not only understand the photodynamics of Chronos and Chronos-expressing neurons but also to design opsins with optimized properties and perform precision experiments with required spatiotemporal resolution.
We present designs of all-optical reversible logic gates, namely, Feynman, Toffoli, Peres and Feynman Double gates,
based on switching of a near-IR (1310/1550 nm) signal by low-power control signals at 532 nm and 405 nm, in optically
controlled bacteriorhodopsin protein-coated silica microcavities coupled between two tapered single-mode fibers.
We present a design of the conservative, reversible, and universal all-optical Fredkin logic gate based on a single bacteriorhodopsin (BR)-protein-coated silica microcavity. The switching of a near-IR laser beam at 1310 or 1550 nm by photoactivating a silica microsphere coated with BR monolayers with a low power control signal at 532 nm, in contact between two tapered single-mode fibers, is used as a template for a four-port tunable resonant coupler Fredkin gate. The proposed gate has also been used to design low-power all-optical AND, OR, NOT, XOR, and X-NOR gates and full-adder and demultiplexer/multiplexer circuits. The advantages of high Q-factor, tunability, compactness, low-power control signals, high fan-out, and flexibility of cascading switches in 2-D to 3-D architectures to form circuits, makes the designs promising for practical applications. The proposed design provides a new paradigm for hybrid nanobiophotonic integration for all-optical computing.
All-optical switching has been theoretically analyzed in LOV2 phototropin, the blue light plant photoreceptor based on nonlinear intensity-induced excited-state absorption. The transmission of a cw probe laser beam at 660 nm through LOV2 protein can be controlled by a cw or pulsed pump laser beam at 442 nm, respectively. This modulation is sensitive to the small-signal absorption coefficient, absorption cross-section of the excited L-state at pump beam wavelength and sample thickness. It is shown that the unique spectral and kinetic properties of wild-type LOV2 and LOV2-C39A mutant, result in the probe beam getting completely switched off (100% modulation), by the pump laser beam of intensity 50 kW/cm2 and 1 kW/cm2, respectively. The switching response in LOV2-WT is faster (~μs) than in LOV2-C39A mutant (~ms). The results have been used to design an optically-addressed spatial light modulator and all-optical NOT, and the universal NAND and NOR logic gates. The results show the applicability of this novel plant photoreceptor protein for photonic applications.
The dynamics of all-optical switching in C60 has been theoretically
analyzed based on the principle of nonlinear intensity-induced
excited-state absorption to achieve high contrast and fast switching. The
transmission of a cw probe laser beam at 885 nm corresponding to the
peak absorption of the S1 state through C60 in toluene is switched by a
pulsed pump laser beam at 532 nm that excites molecules from the
ground state. Switching characteristics are shown to be sensitive to the
variation of pump pulse width, peak pumping intensity, thickness of the
medium, intersystem crossing time between the S1 and T1 states and
the absorption cross section of the S1 state at a probe wavelength, and
their effect are analyzed in detail. It is shown that the transmission of the
probe beam can be completely switched off (100% modulation) by the
pump beam at a pump intensity of 100 MW/cm2 and a pulse width 1.5
ns, with switch on and off times of 2.5 and 7.5 ns, respectively. The
results are used to design all-optical NOT and the universal NOR and
NAND logic gates with multiple pump laser pulses, which are the basic
building blocks of computing circuits.
All-optical switching has been demonstrated in bacteriorhodopsin based on excited-state nonlinear absorption. A probe laser beam at 640 nm corresponding to the O-state absorption maximum is switched due to a strong pulsed pump laser beam at 570 nm, that corresponds to the maximum ground state absorption. We have studied the effect of variation in pulse width and in small signal absorption coefficient on the switching characteristics. The switching time decreases as the pulse width of the pump beam decreases and the small signal absorption coefficient increases. The switching contrast depends mainly on the peak pumping intensity.
We present the general solution of Maxwell's equations for TE modes in a dielectric medium characterized by an intensity dependent dielectric constant of the form ε = ε1 α|E|2 + γ|E|4. The solution is obtained for a bounded fifth-order nonlinear dielectric medium (i.e., for a film) that has been shown to lead in the limiting forms to the known solutions for the unbounded case (i.e., the medium forming a cladding or a substrate) and the solutions for the Kerr case (both bounded and unbounded cases).
We present a simple and accurate . ethod for the analysis of tunneling through an arbitrary onediaensional potential barrier based on the Modified Airy Function approach. We have considered truncated step-linear parabolic and quartic potential barriers. The results have been coipared with those obtained by the conventional WKBJ modified WKBJ and the aatrix sethod. The effect of the truncation level on the tunneling coefficient has also been investigated. I .
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.
