Semiconductor Saturable Bragg Reflector Research Articles

Large-area broad band saturable Bragg reflectors using oxidized AlAs in the circular and inverted mesa geometries

A semiconductor Saturable Bragg Reflector (SBR) is a mirror structure comprising alternating layers of high and low refractive index materials with an incorporated saturable absorber. SBRs can be used to initiate and sustain ultra-short pulses in various laser systems. In order to form ultra-short pulses, SBRs with high reflectivity over a broad wavelength range are required. Furthermore, large-area SBRs facilitate easy integration in a laser cavity. One of the key elements for the realization of broad band SBRs is the development of the thermal oxidation process that creates buried low-index AlxOy layers over large areas. The design, fabrication, characterization, and implementation of broad band, high index contrast III-V/AlxOy SBRs in the form of circular mesas, as well as inverted mesa structures, is presented.

Femtosecond pulse generation around 1500nm using a GaInNAsSb SESAM

The operation of a femtosecond Cr(4+):YAG laser that incorporates a novel GaInNAsSb semiconductor saturable Bragg reflector is reported. In the mode-locked regime 230 fs pulses centred at 1528 nm were generated at an average output power of 280 mW. The SESAM exhibited a low saturation fluence of 10 microJ/cm(2) and a short recovery time of 12 ps.

Coherent control multiphoton processes in semiconductor saturable Bragg reflector with freezing phase algorithm

A freezing phase concept has been proposed for adaptive coherent control with a femtosecond pulse shaper. We applied the scheme to investigate multiphoton processes in InAs quantum dot saturable Bragg reflector (SBR). The optical transition of InAs quantum dots can be revealed in the spectral phase sensitivity plot of second harmonic signal. We also achieved a three-time increase in image contrast on regions with photoluminescent wavelength differing only 18 nm by using coherent control nonlinear optical microscopy. Our results suggest the new freezing phase scheme to be useful for various investigations which require fast and reliable complete-field characterization and coherent control on one setup.

Generation of 90-nJ pulses with a 4-MHz repetition-rate Kerr-lens mode-locked Ti:Al_2O_3 laser operating with net positive and negative intracavity dispersion

We demonstrate the generation of high-energy pulses by using a low-repetition-rate Kerr-lens mode-locked laser. Repetition rates as low as 4 MHz were achieved with a long, multiple-pass cavity and a semiconductor saturable Bragg reflector. The laser generated pulses of 55-fs duration with a pulse energy of 48 nJ when it was mode locked in the net negative dispersion regime. Mode locking in the positive dispersion regime reduces instabilities and enables pulses to have durations of 80 fs and energies as high as 90 nJ. This is, to our knowledge, the highest pulse energy and the lowest repetition rate ever generated directly from a femtosecond laser resonator without cavity dumping.

Synchronously pumped optical parametric oscillation in periodically poled lithium niobate with 1-W average output power

We report on a rugged all-solid-state laser source of near-IR radiation in the range of 1461-1601 nm based on a high-power Nd:YVO(4) laser that is mode locked by a semiconductor saturable Bragg reflector as the pump source of a synchronously pumped optical parametric oscillator with a periodically poled lithium niobate crystal. The system produces 34-ps pulses with a high repetition rate of 235 MHz and an average output power of 1 W. The relatively long pulses lead to wide cavity detuning tolerances. The comparatively narrow spectral bandwidth of <15 GHz is suitable for applications such as pollutant detection.

Self-starting mode-locked Cr:forsterite laser with semiconductor saturable Bragg reflector

We report the self-starting passively mode-locked operation of a chromium-doped forsterite laser using a semiconductor saturable Bragg reflector. Self-starting mode-locking was the only operational mode of the laser and could be achieved with and without intracavity dispersion compensation. We obtained 110 fs transformed limited pulses using a prism pair for dispersion compensation, 4 ps pulses without prisms, and pulse energies of up to 2.3 nJ at 90 MHz repetition rate.

Mode-locking ultrafast solid-state lasers with saturable Bragg reflectors

We discuss mode-locking of low-gain solid-state lasers using a semiconductor saturable Bragg reflector structure. This recently developed low-loss mode-locking device consists of a single quantum well which acts as a saturable absorber incorporated into a high-reflectivity Bragg mirror. Highly stable mode-locking in solid-state lasers results from an ultrafast transient reflectivity in the device that is caused by saturation of the excitonic absorption in near-resonant conditions.