D. Udaiyan

Characterization of a distortion-corrected Nd:YAG laser with a self-conjugating loop geometry

A detailed experimental and theoretical characterization of a self-adaptive solid-state laser is presented. The system uses a saturable gain medium (Nd:YAG amplifier) as the adaptive element in an externally injected self-intersecting loop geometry. We demonstrate energy output >300 mJ, high energy reflectivity >10/sup 4/, low input energy threshold of /spl sim/5 /spl mu/J, and phase-conjugate properties of the system that compensate for both intracavity and extracavity phase distortions. The spatial output beam size is compared to a Gaussian mode analysis based on ABCD ray transfer matrices. The temporal, spectral, energy, and threshold characteristics are compared to one-dimensional analytical and transient numerical simulations.

Transient modelling of double-pumped phase conjugation in inverted Nd:YAG

Abstract Transient modelling of double-pumped phase conjugation (DPPC) in gain media is presented. Numerical results for reflectivity, diffraction efficiency and temporal behaviour of an injected DPPC system and self-starting DPPC laser are discussed. An experimental gain DPPC system and self-starting version are then modelled, and a comparison is made between numerical and experimental results.

Generalized time-dynamics of saturable gain four-wave mixing applied to adaptive laser resonators

Summary form only given. Gain gratings in laser media have been extensively studied to understand gain four-wave mixing (FWM) as a means of achieving phase conjugation, particularly in the steady-state and highly-transient regimes. We present an analysis of the generalized time regime (including pumping and spontaneous emission) and model the time-dependent evolution of the gain grating from the highly transient to the steady-state for arbitrary beam strength. For the first time to our knowledge, this analysis considers the formation of a combined transmission and reflection gain grating.

Spatial control of Gaussian modes in holographic self-adaptive laser oscillators

By using the transfer matrixs method we present an analysis of the transient dynamics of the fundamental mode resonating in a self-adaptive holographic laser oscillator. The resonator consists of a nonlinear medium in a self- intersecting geometry, a lens and an output coupler mirror. We find that the mode exhibits an stable evolution through the self-consistent solutions. Additionally we present useful results for the spatial control of the mode and the improvement of the phase conjugation process.

Spatial Mode Analysis of Self-Adaptive Laser Oscillators

Optical phase conjugation techniques have been widely investigated for the dynamic correction of intracavity phase distortions in laser systems. The beam quality and stability in conventional solid-state lasers can be degraded due to thermally-induced phase distortions in the gain medium [ I ] . This work describes an analysis of the self-consistent fundamental mode of a self-adaptive holographic resonator which can dynamically correct for internal phase distortions [2]. Figure 1 shows a simplified schematic of the system, which incorporates a nonlinear four-wave mixing (FWM) medium (with interacting beams El e) in a self-intersecting loop geometry. Feedback is provided by an output coupler and a loop amplifier provides sufficient gain for the system to reach lasing threshold. A simplified system without intracavity elements is analysed initially and an analytic expression for the mode solution is deduced. Addition of an intracavity lens is shown to allow enhancement of the quality of the phase conjugation process as well as control of the mode size. The theoretical analysis is extended to model an experimental self-adaptive laser oscillator utilising gain-grating formation in a flashlamppumped NdYAG laser amplifier as the nonlinear mechanism. Good agreement is found between the theory and the experimental results. Plane output coupler (OC) n n

Self-starting vector phase conjugate laser oscillator in inverted Nd:YAG

We report the operation of a self-adaptive vector phase conjugate laser (VPCL) oscillator which compensates intracavity polarization distortion and wavefront aberration simultaneously. The VPCL in Nd:YAG gain media produce an output with energy of 125mJ in a 20ns single-longitudinal-mode pulse at 10Hz, which is unaffected by intracavity polarization distortion.

Nd:YAG laser with a ring resonator and a phase-conjugating mirror based on external stimulated Brillouin scattering

We report Q-switching of a Nd:YAG laser with a phase-conjugation mirror based on external external stimulated Brillouin scattering in CS2, using a ring resonator. Pulses with 5 mJ minimum energy and duration of 15 ns, at 2 Hz repetition rate, in the TEM00 mode were generated. A numerical simulation of the Q-switching regime has been made and good agreement between theoretical and experimental data has been obtained.