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We present a generalized model for the photochemical cycle of bacteriorhodopsin bR protein molecule. Rate equations have been solved for the detailed light-induced processes in bR for its nine states: $(B\rightarrow K \leftrightarrow L \leftrightarrow M^I \rightarrow (M^{II}) \leftrightarrow N \leftrightarrow$ $O \leftrightarrow P \rightarrow Q \rightarrow B)$. The complete steady-state intensity-induced population densities in various states of the molecule have been computed to obtain a general, exact, and analytical expression for the nonlinear absorption coefficient for multiple modulation pump laser beams. All-optical light modulation of different probe laser beam transmissions by intensity induced population changes due to one and two modulation laser beams has been analyzed. The proposed model has been shown to accurately model experimental results.

A simplified energy‐level scheme is proposed for the photochemical cycle of the bacteriorhodopsin molecule. Rate equations are solved for the detailed light‐induced processes based on this model and the intensity‐induced population densities in various states of the molecule at steady state are computed which are used to obtain an analytic expression for the absorption coefficient of the modulation beam. Modulation of the probe laser‐beam transmission by the modulation‐laser‐beam intensity‐induced population changes is analyzed. It is predicted that for a probe beam at 412 nm up to 82% modulation can be achieved using a laser beam intensity of 3.2 W/cm2 at 570 nm. For temperatures ∼77 K, the transmission at 610 nm can be switched from zero to 81% for modulating laser intensity of 11 W/cm2. Construction of a spatial light modulator based on bacteriorhodopsin molecules is proposed and some of its features are discussed.

Spatial light modulation based on nonlinear absorption of light by excited-state molecules in C60–toluene solution is demonstrated. Amplitude modulation of probe laser beam transmissions at 747 and 885 nm, corresponding to the peak absorption of T1 and S1 states, by the modulation laser beam intensity induced population changes at 532 nm has been analyzed using the rate equation approach, for various values of the small-signal absorption coefficient. It is shown that for T1 and S1 states, modulation up to 100% and 94.5% can be achieved for a laser beam intensity of 800 W/cm2 and 1 kW/cm2 at 532 nm, respectively.

The power generation in a gasdynamic laser (GDL) has been theoretically studied. Quasi-one-dimensional unsteady flow equations are numerically solved simultaneously with the rate equation for the laser intensity inside the laser cavity. Steady-state coupled solutions for the field variables and the laser intensity inside the GDL cavity are obtained by a time-dependent numerical technique. The laser intensity variations along the axis of the flow (across the laser cavity) are computed for different laser gas mixture compositions and reservoir conditions. The analysis predicts a sharp spike in the laser intensity at the leading edge of the laser cavity followed by a sharp fall from which it recovers to a uniform constant value for the lower $H_20$ concentrations. It is shown that the $H_20$ concentration above 2% in the $CO_2-N_2-H_20$ gas mixture is detrimental to he power generation.

The propagation of a normal shock wave into the CO2‐N2‐He gas mixture seeded with solid particles is analyzed. The translation‐vibration and vibration‐vibration molecular energy exchange processes in the gas mixture are included in the analysis. The results indicate the creation of population inversions due to these processes in the relaxation region behind the shock wave for transitions at 50 and 22 μm in CO2 molecules. The presence of solid particles in the flow is found to be advantageous for observing the laser radiation behind the shock wave. Effects of the frozen shock Mach number, the particle size, the particle‐to‐gas mass loading ratio, and the laser gas mixture composition on the population inversions are discussed.

Passive mode locking of lasers using the protein molecule bacteriorhodopsin which acts as a slow saturable absorber is proposed. Based on the self‐consistent approach, expressions for the laser pulse energy and pulsewidth are derived. It is shown that mode‐locked pulses of 64 fs duration and 7 nJ energy could be generated in the visible region by this method.

Theoretical analysis of internal frequency doubling in actively mode locked broadband solid state lasers is presented. The analysis is used to study the dependence of mode locked pulsewidth on the second harmonic conversion efficiency, the modulation depth, and the tuning element bandwidth in an AM mode locked Ti: sapphire laser. The results are presented in the form of graphs.

The generation of a 16 μm laser beam through cascading in a downstream‐mixing CO2 gasdynamic laser is studied. To simulate actual lasing action, a generalized, two‐dimensional, flow‐radiation‐coupled power extraction model for a gasdynamic laser is used. Also, to model the cascade process a new four‐mode CO2‐N2 vibrational kinetic model has been proposed. The steady‐state intensity obtained for an exclusive 9.4 μm transition is of the order of 5×107 W/m2. In the cascade mode of operation the steady‐state intensities for 9.4 and 16 μm transitions of the order of 5×107 W/m2 and 1.0×106 W/m2, respectively, have been obtained.

The analysis of propagation of a normal shock wave in CO2‐N2‐He or H2 or H2O system seeded with solid particles is presented. The variation of translational and vibrational temperatures of gas phase and the particle temperatures in the relaxation zone behind the shock front are given in graphical form. These results show that the peak value of population inversion and the width of the inversion zone are highest for He catalyst and lowest for H2O catalyst.

Based on a method proposed by Reddy and Shanmugasundaram, similar solutions have been obtained for the steady inviscid quasi‐one‐dimensional nonreacting flow in the supersonic nozzle of CO2–N2–H2O and CO2–N2–He gasdynamic laser systems. Instead of using the correlations of a nonsimilar function NS for pure N2 gas, as is done in previous publications, the NS correlations are computed here for the actual gas mixtures used in the gasdynamic lasers. Optimum small‐signal optical gain and the corresponding optimum values of the operating parameters like reservoir pressure and temperature and nozzle area ratio are computed using these correlations. The present results are compared with the previous results and the main differences are discussed.

A new method for producing simultaneous lasing at 10.6 μm and 38.3 μm in a CO2‐N2‐CS2 gasdynamic laser is presented. The theoretical analysis predicts small‐signal gain values of the order 0.21 m−1 for 10.6 μm lasing in CO2 molecules and 0.085 m−1 for 38.3 μm lasing in CS2 molecules, indicating the possibility of dual wave lasing.