Motoyuki Watanabe

Picosecond time-resolved near-IR spectra of C60 excited states by pump-probe measurements using a probe beam based on broad-band optical parametric generation

Picosecond time-resolved absorption spectra of C60 singlet and triplet excited states are observed in the near-IR region in the region 700–1300 nm by the pump-probe technique using a probe beam based on broad-band optical parametric generation (OPG) in β-barium borate (BBO) pumped by a picosecond laser pulse at 532 nm and using an InGaAs multichannel detector.

Two-Dimensional Sweeps Expanding Capability And Application Of Streak Cameras

New two-dimensional sweeps of streak cameras; elliptical and high-dense sine-curve scans, have been demonstrated to be an excellent and useful method expanding its performance and application. These have been accomplished by applying a sinusoidal or ramp voltage to the second deflection (horizontal) plate of a synchroscan streak tube. The elliptical scan has enabled direct and time-resolved spectroscopic measurement of highly repetitive optical-pulses in the range of several gigaherts and long decay times in the order of one-half the sweep period. The high-dense sine-curve scan has allowed measurement of fluctuations of pulse-shapes and pulse-intervals in a highly repetitive pulse train, and jitter among driving signals of a mode-locker, pumping pulses and oscillating pulses of an actively mode-locked dye laser.

Application of picosecond time resolved photoluminescence mapping for the characterization of semi-insulating GaAs wafers

Abstract Decay of the band-edge photoluminescence (PL) from semi-insulating GaAs wafers and two-dimensional maps of the PL decay time and PL intensity of a wafer on a picosecond time scale were measured at room temperature using systems which consist of a synchronously pumped dye laser, a laser diode and a streak camera. The temporal trace of the PL was separated into at least two different decay components with decay times of about 40 and 150 ps, respectively. Two-dimensional maps of the band-edge PL decay time for semi-insulating GaAs wafers have been successfully obtained using a streak camera combined with a laser diode driven by a short pulse current. PL decay time gradually varied over the wafer in reasonable association with the PL intensity. Most significant changes in decay time and PL intensity were seen around the scratch on the wafers.

Picosecond fluorescence microscopy

A new picosecond time-resolved fluorescence microscope (PFM) has been developed for measuring and mapping the lifetime of laser excited fluorescence from a sample placed under a micro— scope. A compact laser diode is used to generate excitation pulses. The combination of a spectrograph and a streak camera performs time resolved fluorescence spectroscopy with a resolution of 40 ps ( 5 ps with deconvolusion). The lifetime and the intensity of laser excited fluorescence are analyzed b a computer and are displayed on a monitor as either a lifetime or intensity map.