Hitoshi Tomita

Femtosecond pulse amplification by a two-photon arranged photorefractive amplifier

Femtosecond pulse amplification by a two-photon arranged photorefractive amplifier (TAPA) has been demonstrated. A gain bandwidth of 32 THz has been achieved with an extraction efficiency of 27 %.

All-optical temporal phase correction scheme for few-cycle optical pulses using diffractive optics

All-optical phase correction scheme for few-cycle optical pulses has been proposed. The temporal phase structure of a phase-modulated pulse is recorded as spatial index modulation in a two-photon recording medium. This scheme drastically relaxes complicacy in stretcher design for few-cycle chirped pulse amplification (CPA) systems.

Wide-time-range spectral-shearing interferometry

A long-time-range spectral-shearing interferometry has been demonstrated by frequency mixing with two-color monochromatic fields. Strongly chirped pulses with quadratic and cubic phase distortion have been characterized. A linearly chirped pulse having 2.2 ps (full duration of 6 ps) has been measured with a coaxial two-color field generated by a narrow-gap passive etalon. Substantial extensions in the time range can be expected with a highly coherent two-color source, i.e., frequency stabilized lasers, or two longitudinal modes in the frequency comb.

Femtosecond pulse recoding and self-regeneration in a two-photon gated periodic diffractive optics

A new scheme for pulse recording, time-reversed playback, and self-regeneration in a diffractive device was proposed. Self-pulse-regeneration in a two-photon-recorded glass tip has been demonstrated.

Wide Temporal Coverage Spectral Shearing Interferometer with a Dual Frequency Mixer

We have proposed a replica-free spectral shearing interferometer with a dual frequency local oscillator that warrants fixed frequency shift and wide temporal coverage. We applied this technique to characterize few-cycle and several-ps optical pulses.

Frequency-domain Phase Conjugator for a Few-cycle and a Few-nJ Optical Pulses

Temporal phase structure of a 10-fs optical pulse has been regenerated by frequency-domain phase conjugator based on the two-photon recorded Bragg diffraction. This optically programmable diffractive device with the index modulation of Δn = 0.03 was directly written by a mode-locked laser with no cavity extension.

Wide-range spectral shearing interferometry

A new scheme of spectral shearing interferometer providing a wide observation window has been demonstrated. Few-cycle pulse has been measured with a temporal observation/resolution ratio of ≫10³ and a dynamic range of ≫10⁸.

High-resolution spectral-shearing interferometry

We present spectral-shearing interferometry with a high group-delay resolution that is defined as a ratio of the maximum temporal window and the shortest pulse duration. This technique allows the resolution of 104.

Automatic compensation of higher order dispersion in chirped pulse amplification system by a nonlinear-recorded diffractive optics

All-optical phase-correction scheme in a 10 fs CPA system using a frequency-domain phase conjugator (FDPC) has been proposed. The cubic and quadratic phase distortions are automatically eliminated by an optically programmable pre-compensator.

Spectral shearing interferometer with frequency- and time-resolved sum-frequency mixing

A two-dimensional spectral-shearing interferogram has been acquired instantaneously by frequency- and time-resolved sum-frequency conversion where the phase-matching angle and transverse-delay of crossed-pump beams in a nonlinear crystal serve as frequency-time decomposed imaging. The two spectrally sheared components travel the same path after upconversion. A picoseconds delay-scanned interferogram is accumulated on a 2D image sensor.