Michiyuki Endo

Temperature-dependent Sellmeier coefficients and chromatic dispersions for some optical fiber glasses

Temperature-dependent Sellmeier coefficients are necessary to optimize optical design parameters of the optical fiber transmission system. These coefficients are calculated for fused silica (SiO/sub 2/), aluminosilicate, and Vycor glasses for the first time to find the temperature dependence of chromatic dispersion at any wavelength from UV to 1.7 /spl mu/m. The zero dispersion wavelength /spl lambda//sub 0/ (1.273 /spl mu/m for SiO/sub 2/, 1.393 /spl mu/m for aluminosilicate, and 1.265 /spl mu/m for Vycor glasses at 26/spl deg/C) varies linearly with temperature, and d/spl lambda//sub 0//dT is 0.03 nm/K for aluminosilicate and Vycor glasses, whereas for SiO/sub 2/ it is 0.025 nm/K. This study interprets the recently observed experimental value of d/spl lambda//sub 0//dT for two dispersion shifted optical fibers; and the dominantly material origin of d/spl lambda//sub 0//dT is confirmed here as a fundamental property of the optical fiber glasses. >

Automatic Calibration System for a Laser Power Meter

A microprocessor-based calibration system for a CW laser power meter has been developed. The system consists of an isothermal calorimeter with a thermopile unit, an electrical, and an optical subsystem. Temperature control of the thermopile unit is achieved through a digital technique. The calibration of a power meter is performed using the effective efficiency of the unit as measured by a calorimeter. From error analyses, an overall accuracy has been obtained as ±1 percent in root mean square for a power level of 1 ~ 200 mW.

A double calorimeter for 10-W level laser power measurements

A new type calorimeter for precise measurement of 10-W level laser power has been fabricated. This is a double configuration consisting of an absorbing unit made of a disk absorber and an isothermal type calorimeter. These components have a fast response and high accuracy. The principle of the measurement is based on the dc substitution method. The ratio of the substituted laser power to the dc power is determined by the absorbing unit. The basic structure of the system and preliminary experimental results are described. The time constant of the absorbing unit is shorter than 0.4 s. The effective efficiency of the unit is 94.0-94.1% with a standard deviation of 0.15% in the range from l to 10 W at 10.6 /spl mu/m wavelength using a CO/sub 2/ laser.

Measurements of picosecond laser pulses from mode-locked Nd:YAG laser

This paper deals with measurements of picosecond laser pulse parameters such as temporal and spatial profile, and power. Pulseshape measurements were conducted by using the combined streak camera and optical multichannel analyzer system. The precision of measurements are discussed.

Attenuation-Measurement Technique With a Small Mismatch Uncertainty Using Phase Characteristics of Multiple Reflected Signals

An accurate radio-frequency and microwave attenuation-measurement technique with a small mismatch uncertainty for continuous-frequency application has been developed by shifting the phase characteristics of the multiple reflected signals. A loss-measurement system in four different phase networks is set for this purpose by introducing two low-reflective lines (airlines) where the phase-shift values are already known. From substitution-loss measurements carried out for variable attenuators as devices under test, the attenuation is simply obtained, which is unrelated to the source and load reflection coefficients of ΓG and ΓL, respectively. Experimental measurements on a 10-dB step attenuator performed with a 40-mm length of airlines at almost continuous frequencies from 12.3 to 14.1 GHz are demonstrated and show a good agreement with measurements where the test ports are impedance-matched.

Adaptive multifrequency modulation method for an advanced laser range finder

The intensity of a laser beam is modulated with radio frequencies (RF), in a laser range finder. The modulated laser beam is directed to a target, and the reflected light is detected. The phase of the RP signal from the detector is measured. A semitransparent obstacle between the laser and the target degrades the accuracy of the range measurement. In this paper, an adaptive multifrequency modulation method is proposed and experimentally verified to overcome this problem. >

Generation of Tunable Pulses below 345 fs Using a Passively Mode-Locked Fiber Ring Laser with Bulk Components.

A stable, passively mode-locked erbium-doped silica fiber ring resonator is fabricated to generate tunable optical pulses with durations of 270–345 fs in the 1.55 µ m band pumped by a 1.48 µ m semiconductor laser diode. The lasing wavelength is tuned continuously over a wavelength range of 60 nm from 1.532 to 1.594 µ m by rotating a bulk band-pass filter inserted in the resonator with a repetition rate of 45.4 MHz.

A wide-band RF activated electrooptic laser beam modulator

A wide-band optical modulator for laser beam is designed and constructed. The velocity-matching between the laser beam and the RF wave is realized in a partially-loaded micro-strip line structure to achieve 10 GHz bandwidth.<<ETX>>

Timing Jitter Reduction in a Passively Mode-Locked Fiber Laser

We generated laser pulses of 270 fs in the 1.55 µ m band with a repetition rate of 45.4 MHz in a passively mode-locked, erbium-doped fiber ring laser, pumped by a laser diode. We reduced the timing jitter by minimizing the intensity fluctuation of the pump source using a feedback loop and by controlling the air fluctuation of the laser resonator in a sealed box. The rms timing jitter is below 0.9 ps in the range of 30–3000 Hz.

Picosecond optical pulse measurement based on an electro-optic sampling technique

Ultrafast single-shot optical pulse waveform measurement has been investigated by an electrooptic sampling technique. A traveling-wave Pockels cell crystal driven by an ultrafast photoconductive switch was employed as a sampler. An optical pulse compression system following a pulsed Nd-YAG laser was used as a sampling probe pulse generator. Basic experiments of the sampling were performed and the temporal resolution was found to be 18 ps. >