Rintaro Koda

300 W Peak Power Picosecond Optical Pulse Generation by Blue-Violet GaInN Mode-Locked Laser Diode and Semiconductor Optical Amplifier

We have generated picosecond optical pulses with a peak power greater than 300 W at 1 GHz repetition at a blue-violet wavelength using a GaInN-based master oscillator power amplifier. The optical pulses were generated by a mode-locked laser diode incorporating the flared waveguide structure for the increased active region volume to obtain higher output power. The pulses were effectively amplified by the semiconductor optical amplifier with reduced optical confinement factor to high peak power.

140-fs duration and 60-W peak power blue-violet optical pulses generated by a dispersion-compensated GaInN mode-locked semiconductor laser diode using a nonlinear pulse compressor

Blue-violet optical pulses of 140-fs duration and 60-W peak power were obtained from a dispersion-compensated GaInN mode-locked semiconductor laser diode using a nonlinear pulse compression technique. Wavelength-dependent group velocity dispersion expressed by third-order phase dispersion was applied to the optical pulses using a pulse compressor with a spatial light modulator. The obtained optical pulses had the shortest duration ever obtained for a mode-locked semiconductor laser diode using edge-emitting type devices.

Direct generation of 20 W peak power picosecond optical pulses from an external-cavity mode-locked GaInN laser diode incorporating a flared waveguide

We directly generated 1.6-ps optical pulses with a peak power of 20 W at a repetition of 1 GHz using a blue-violet GaInN mode-locked laser diode incorporating a flared waveguide operating in single transverse mode. The flared waveguide enabled optical pulses to be generated with peak powers of over six times higher than those produced using a straight waveguide while preserving the pulse duration.

Lateral optical confinement of GaN-based VCSEL using an atomically smooth monolithic curved mirror

We demonstrate the lateral optical confinement of GaN-based vertical-cavity surface-emitting lasers (GaN-VCSELs) with a cavity containing a curved mirror that is formed monolithically on a GaN wafer. The output wavelength of the devices is 441–455 nm. The threshold current is 40 mA (Jth = 141 kA/cm2) under pulsed current injection (Wp = 100 ns; duty = 0.2%) at room temperature. We confirm the lateral optical confinement by recording near-field images and investigating the dependence of threshold current on aperture size. The beam profile can be fitted with a Gaussian having a theoretical standard deviation of σ = 0.723 µm, which is significantly smaller than previously reported values for GaN-VCSELs with plane mirrors. Lateral optical confinement with this structure theoretically allows aperture miniaturization to the diffraction limit, resulting in threshold currents far lower than sub-milliamperes. The proposed structure enabled GaN-based VCSELs to be constructed with cavities as long as 28.3 µm, which greatly simplifies the fabrication process owing to longitudinal mode spacings of less than a few nanometers and should help the implementation of these devices in practice.

9-kW peak power and 150-fs duration blue-violet optical pulses generated by GaInN master oscillator power amplifier

Blue-violet optical pulses of 9-kW peak power and 150-fs duration were obtained from a GaInN master oscillator power amplifier system using a nonlinear dispersion compensator. Seed pulses from a dispersion-compensated GaInN mode-locked semiconductor laser diode were stretched to 3-ps duration using a nonlinear dispersion compensator with a spatial light modulator that added second-order phase dispersion to an optimized nonlinear phase dispersion compensating the higher-order dispersion of the optical pulses. The stretched phase-optimized pulses were efficiently amplified to 3.0 nJ by a GaInN semiconductor optical amplifier. The amplified pulses were subsequently compressed using a linear pulse compressor, yielding 1.4-nJ femtosecond pulses. The obtained results show the highest peak-power ever reported for an electrically-pumped semiconductor gain medium.

Nonlinear compression of optical pulses at 400 nm from a GaInN mode-locked semiconductor laser diode yielding 140-fs duration and 60-W peak-power optical pulses

Ultrashort optical pulses of 140-fs duration and 60-W peak power were obtained at 400 nm from a dispersion-compensated GaInN mode-locked semiconductor laser diode using a nonlinear pulse compressor consisted of a spatial light modulator.

Blue Femtosecond Laser Diode Systems

Ultrafast laser systems based on GaInN semiconductor laser diodes are developed to generate high-peak power ultrashort optical pulses for practical applications. Progress of femtosecond pulse generation using mode-locked GaInN laser diode is reported.