Masaki Tokurakawa

Diode-pumped ultrashort-pulse generation based on Yb 3+ :Sc 2 O 3 and Yb 3+ :Y 2 O 3 ceramic multi-gain-media oscillator

Diode-pumped mode-locked laser operation based on Yb(3+):Sc(2)O(3) and Yb(3+):Y(2)O(3) multi-gain-media oscillator has been demonstrated. 66-fs pulse duration with an average power of 1.5 W and 53-fs pulse duration with an average power of 1 W under 8-W laser diode pumping were achieved. The optical-to-optical efficiency was 18.8%. Additionally, 68-fs pulse duration with an average power of 540 mW from Yb(3+):Y(2)O(3) ceramic was also obtained.

Diode-pumped 65 fs Kerr-lens mode-locked Yb(3+):Lu(2)O(3) and nondoped Y(2)O(3) combined ceramic laser.

Diode-pumped Kerr-lens mode-locked laser operation of Yb(3+):Lu(2)O(3) and nondoped Y(2)O(3) combined ceramics has been achieved; 65 fs pulses with an average power of 320 mW under 5 W of pump power were obtained at the center wavelength of 1032 nm. The spectral bandwidth and the time bandwidth product were 18.9 and 0.345 nm, respectively. To our knowledge, this is the first demonstration of a Kerr-lens mode-locked laser operation based on Yb(3+):Lu(2)O(3) ceramic.

Diode-pumped sub-100 fs Kerr-lens mode-locked Yb3+:Sc2O3 ceramic laser.

Diode-pumped Kerr-lens mode-locked laser operations of Yb3+:Sc2O3 ceramics have been achieved. 92 fs pulses with the average power of 850 mW under 3.89 W incident pump power were obtained at a center wavelength of 1042 nm. The optical-to-optical efficiency was 21.9%. 90 fs pulses with the average power of 160 mW were also obtained at a center wavelength of 1092 nm. To our knowledge, this is the first demonstration of a Kerr-lens mode-locked Yb3+:Sc2O3 laser.

Diode-pumped 188fs mode-locked Yb3+:Y2O3 ceramic laser

The authors have demonstrated a diode-pumped passively mode-locked Yb3+:Y2O3 ceramic laser by use of a semiconductor saturable absorber mirror. 188fs pulses at a center wavelength of 1038nm are obtained. The maximum output power is 220mW at an absorbed pump power of 2.4W with a diffraction-limited beam quality (M2<1.1). This is the shortest pulse generation from Yb-doped sesquioxide lasers and ceramic lasers ever reported.

High resolution Fourier domain optical coherence tomography in the 2 μm wavelength range using a broadband supercontinuum source.

A 220 nm bandwidth supercontinuum source in the two-micron wavelength range has been developed for use in a Fourier domain optical coherence tomography (FDOCT) system. This long wavelength source serves to enhance probing depth in highly scattering material with low water content. We present results confirming improved penetration depth in high opacity paint samples while achieving the high axial resolution needed to resolve individual paint layers. This is the first FDOCT developed in the 2 μm wavelength regime that allows fast, efficient capturing of 3D image cubes at a high axial resolution of 13 μm in air (or 9 μm in paint).

Ultra-short wavelength operation of a thulium fibre laser in the 1660–1750 nm wavelength band

Ultra-short wavelength operation of a thulium fibre laser is investigated. Through use of core pumping and high feedback efficiency wavelength selection, a continuously-tunable fibre laser source operating from 1660 nm to 1720 nm is demonstrated in a silica host. We discuss the range of applications within this important wavelength band such as polymer materials processing and medical applications targeting characteristic C-H bond resonance peaks. As a demonstration of the power scalability of thulium fibre lasers in this band, fixed wavelength operation at 1726 nm with output power up 12.6 W and with slope efficiency > 60% is also shown.

Continuous Wave and Mode-locked Yb3+:Y2O3 Ceramic Thin-disk Laser

CW and mode-locked laser operation based on an Yb3+:Y2O3 ceramic thin disk is reported. In CW laser operation, an output power of 70 W with an optical-to-optical efficiency of 57.4% was achieved. A higher slope efficiency of 70% was also obtained with a 50-W pump laser diode with more suitable emission characteristics. In mode-locked laser operation, pulses as short as 547 fs with an average power of 7.4 W were obtained. To our knowledge, this is the first demonstration of a high power CW and mode-locked laser operation based on Yb3+:Y2O3 ceramic thin disks.

Optical coherence tomography in the 2-μm wavelength regime for paint and other high opacity materials

An optical coherence tomography system using a compact fiber source emitting amplified spontaneous emission at central wavelength of 1960 nm with bandwidth of 40 nm is developed to enhance the probing depth in a highly scattering material with low water content. Examples of application to paint are used to demonstrate significantly improved penetration depth in high opacity materials in the 2-μm wavelength regime.

Ultrashort pulse generation from diode pumped mode-locked Yb 3+ :sesquioxide single crystal lasers

We present diode pumped SESAM supported Kerr-lens mode locked laser operation based on Yb3+:Sc2O3 and Yb3+:Lu2O3 single crystals. Pulses as short as 71 fs with an average power of 1.09 W were obtained from an Yb3+:Lu2O3 single crystal. Yb3+:Sc2O3 delivered pulses as short as 81 fs with an average power of 840 mW. The mode locked laser operation was stable for longer than 2 hours.

Exploiting the short wavelength gain of silica-based thulium-doped fiber amplifiers

Short wavelength operation (1650-1800 nm) of silica-based thulium-doped fiber amplifiers (TDFAs) is investigated. We report the first demonstration of in-band diode-pumped silica-based TDFAs working in the 1700-1800 nm waveband. Up to 29 dB of small-signal gain is achieved in this spectral region, with an operation wavelength accessible by diode pumping as short as 1710 nm. Further gain extension toward shorter wavelengths is realized in a fiber laser pumped configuration. A silica-based TDFA working in the 1650-1700 nm range with up to 29 dB small-signal gain and noise figure as low as 6.5 dB is presented.