Shinji Izumida

High average-power THz radiation from femtosecond laser-irradiated InAs in a magnetic field and its elliptical polarization characteristics

The THz-radiation power from bulk InAs irradiated with femtosecond optical pulses is significantly enhanced and reaches 650 μW in a 1.7-T magnetic field with 1.5-W excitation power. The THz-radiation power is related almost quadratically both to the magnetic field and excitation laser power. We have also found that the power of the THz-radiation from an InAs sample in a magnetic field is over one order of magnitude higher than that from GaAs. Additionally, a dramatic change of ellipticity is observed, and the spectra of the horizontal and vertical polarization components are found to differ.

Growth and ultraviolet application of Li2B4O7 crystals: Generation of the fourth and fifth harmonics of Nd:Y3Al5O12 lasers

A 2 in. diam single crystal of lithium tetraborate (Li2B4O7) was successfully grown by the Czochralski method. The crystal was free from macrodefects and had a dislocation density as low as 100/cm2. It had an excellent homogeneity of the refractive index and a wide transparency down to 170 nm. The optical damage threshold was 40 GW/cm2. Second-harmonic generation and sum frequency generation were investigated in association with the generation of the fourth and fifth harmonics of a Q-switched Nd:YAG laser. The conversion efficiency of the second-harmonic generation from the green (532 nm) light was 20%.

Spectrum control of THz radiation from InAs in a magnetic field by duration and frequency chirp of the excitation pulses

The THz radiation spectrum from InAs in a magnetic field irradiated with femtosecond pulses can be controlled by varying the excitation pulse width and chirp direction of the excitation pulse. A longer excitation pulse width produces lower-frequency THz radiation. Also, positively chirped pulse excitation will generate higher power and higher frequency THz radiation.

All-Solid-State Tunable Ultraviolet Subnanosecond Laser with Direct Pumping by the Fifth Harmonic of a Nd:YAG laser.

We report what we believe is the first all-solid-state tunable ultraviolet laser pumped by the fifth harmonic of a Q-switched Nd:YAG laser. Our laser based on a Ce(3+):LiLuF(4) active medium stably generates a single, satellite-free, 0.88-ns pulse under 5-ns, 10-Hz repetition rate pumping conditions. A novel tilted-incident-angle side-pumping scheme resulted in a simple laser-cavity design.

High-Pulse-Energy, All-Solid-State, Ultraviolet Laser Oscillator Using Large Czochralski-Grown Ce:LiCAF Crystal

A large Ce3+:LiCaAlF6 (Ce:LiCAF) crystal of 15 mm diameter was grown successfully by the Czochralski method. Owing to its large size, the Ce:LiCAF crystal demonstrated a maximum output pulse energy from the Ce:LiCAF laser of 21 mJ at a wavelength of 290 nm with an absorbed pump energy of 54 mJ from the fourth harmonic of a Q-switched Nd:YAG laser operated at a 10-Hz repetition rate. Furthermore, the lasing threshold was a low 12 mJ, and the slope efficiency was 39%.

All-Solid-State, THz Radiation Source Using a Saturable Bragg Reflector in a Femtosecond Mode-Locked Laser

We have demonstrated a new scheme for generating intense far-infrared or THz radiation pulses synchronously with near-infrared pulses using a saturable Bragg reflector placed inside a mode-locked laser cavity. With this newly proposed simple scheme, THz radiation which peaked at around 0.66 THz, with an average power of 2–3 nW is directly generated synchronously with femtosecond near-infrared optical pulses.

High-repetition-rate, high-average-power, mode-locked Ti:sapphire laser with an intracavity continuous-wave amplification scheme

We have demonstrated a high-average-power, mode-locked Ti:sapphire laser with an intracavity continuous-wave amplification scheme. The laser generated 150 fs pulses with 3.4 W average power at a repetition rate of 79 MHz. This simple amplification scheme can be applied for the power scaling of other lasers.

INTENSE THz-RADIATION SOURCES USING SEMICONDUCTORS IRRADIATED WITH FEMTOSECOND LASER PULSES IN A MAGNETIC FIELD

We report significant enhancement of THz radiation from InAs under magnetic field irradiated with femtosecond pulses. The THz-radiation power is significantly enhanced and reaches sub-mW level in a 1.7-T magnetic field with 1.5-W excitation power. The THz-radiation power is related almost quadratically both to the magnetic field and excitation laser power. Furthermore, the radiation spectrum is found to be controlled by the excitation pulsewidth, chirp direction of the excitation pulse, and the magnetic field. Additionally, we have demonstrated a new method to generate THz radiation from a saturable Bragg reflector in a magnetic field.

Intense THz-radiation from semiconductors under magnetic field irradiated with femtosecond laser pulses

The THz-radiation power from InAs reaches sub-mW level in a 1.7-T magnetic field irradiated with femtosecond laser pulses of 1.5-W average power. The THz-radiation power is related almost quadratically both to the magnetic field and to the excitation laser power. Furthermore, the THz-radiation spectrum is found to be controlled by the excitation pulsewidth, chirp direction of the excitation pulse, and the magnetic field.

Significant enhancement of the THz radiation from an InAs (100) clean surface at low-temperature

Summary form only given. We report the strong enhancement of THz radiation from an InAs irradiated with femtosecond laser pulses after surface cleaning and cooling.