Study of operation dynamics for crystal temperature measurement in a diode end-pumped monolithic Yb:YAG laser.

A temperature measurement scheme was proposed in a diode end-pumped thin monolithic Yb:YAG laser by analyzing the red-shifting behaviors of each lasing peak. The amount of peak shift was measured on the basis of the threshold lasing spectrum by using a chopped pump beam. In order to determine the effective scale factor, the ratio between the peak shift and the temperature rise, the dynamics of the spectral shift, the output beam profile, and the output power were investigated. The effective scale factor was determined to be about 0.0114 nm/°C in the case of the crystal sandwiched by copper bocks with a hole, wherein the plane stress approximation is valid. On the other hand, the effective scale factor significantly decreased in the case of the crystal sandwiched by sapphire plates.

Resonant characteristics of multimode interferometer coupled square ring semiconductor resonators.

This work reports the spectral characteristics of coupled square ring semiconductor resonators. For a single mode operation, the square ring cavities coupled with multimode interferometers (MMIs) are proposed and fabricated using the epitaxial layers of 1.55 microm center wavelength InGaAsP-InP multiple quantum wells. Resonant characteristics can be tailored by varying the parameters of the cavity size or the waveguide width. By using the MMI coupled square ring cavity, a stable single spectral lasing mode was obtained in various combinations of square cavities.

Strongly enhanced mode selection in a thin dielectric-coated layered microcavity laser.

Strong mode selection through an enhanced interferential coupling effect was observed in a thin dielectric-coated layered cylindrical microcavity laser. The strong coupling effect was induced owing to an enhanced reflectivity of around 50% at the dielectric-coated inner boundary of a fused silica capillary filled with a dye-doped liquid. At an optimized coating thickness of about 0.4 microm, the lasing peaks appeared only at the wavelengths corresponding to the constructive interference condition, whereas those from a bare capillary were weakly modulated.

Diode-pumped 100-W green Nd:YAG rod laser.

We developed a diode-pumped high-average-power Nd:YAG green laser. By use of a monolithic diffusive reflector having three slits and a rod with low doping concentration, uniform distribution of excited Nd ions could be achieved. Uniform distribution in the rod reduced thermal birefringence. We employed a Z-shaped cavity to have a constant beam size at the frequency-doubling crystal independent of thermal lensing in the rod. The pulse width and green power dependence on the pump power were analyzed. A maximum green power of 101 W was obtained when the total pump power was 398 W. The optical-to-optical conversion efficiency was as high as 25.4%.

Observation of scarred modes in asymmetrically deformed microcylinder lasers.

We report observation of lasing in the scarred modes in an asymmetrically deformed microcavity made of liquid jet. The observed scarred modes correspond to morphology-dependent resonance of radial mode order 3 with their Q values in the range of 10(6). Emission directionality is also observed, corresponding to a hexagonal unstable periodic orbit.

Design and fabrication of a diode-side-pumped Nd:YAG laser with a diffusive optical cavity for 500-W output power.

A ray-tracing code has been developed, and the design parameters of the laser pump head were analyzed in terms of crystal diameter, doping concentration, and optical cavity diameter. According to the numerical analysis, we fabricated an efficient diode-pumped Nd:YAG laser and experimentally obtained 500-W output power. The output power is close to the numerically calculated output power of approximately 450 W and corresponds to an optical-to-optical conversion efficiency of 46.7% and an optical slope efficiency of 49%.