Y. Ida

Simple method for measuring the linewidth enhancement factor of semiconductor lasers by optical injection locking.

A simple method for measuring the linewidth enhancement factor alpha of a semiconductor laser by optical injection locking is described. Without knowledge of the absolute values of detuning and the optical injection level, the value of alpha is evaluated from only changes in optical power in the stable optical injection-locking state. The value of alpha of a 0.83-microm channeled substrate planar laser is evaluated to be 2.65 +/- 0.2. The measurement error of this method is also discussed.

Reflection-type delayed self-homodyne/heterodyne method for optical linewidth measurements

The reflection-type delayed self-homodyne (RDSH) method presently described is based on the same principle as the delayed self-homodyne/heterodyne (DSH) method but no beam splitter or fiber coupler is required. The delayed beam is produced by utilizing a round-trip propagation passing through a solitary long optical fiber delay line. Therefore, the optical configuration is very simple, and the beat signal has a resolution twice that of the DSH method. However, the RDSH methods drawback is that a large intensity difference between the two beams reduces the level of the beat signal. This can be improved by increasing the reflectivities of the fiber ends by dielectric coating. In this case, multiple reflection at the fiber ends should be taken into account. >

ANALYTICAL AND EXPERIMENTAL STUDY ON LANDAU DAMPING OF SURFACE WAVE ALONG A PLASMA COLUMN.

A resonator method is used to demonstrate Landau‐damping of surface waves along a plasma column. As a method of plasma diagnostics, an open plasma resonator utilizing longitudinal resonance of the surface wave has been proposed by one of us. This work presents an analysis of anomalous damping in terms of the Q factor observed in the open plasma resonator. In the analysis, the effect of energy absorption by the thermal electrons travelling across the side boundaries of the resonator is accounted for. A method of single‐mode excitation which is convenient for experimental determination of the Q factor is also described. The results of Q measurements are compared with the computer solutions; the Landau‐damping mechanism which is responsible for the anomalous damping in the Q factor is examined.

Experimental determination of gain compression factors of a DFB laser in the presence of TM light injection

Compared to direct current modulation, an optical modulation scheme of laser diodes exhibits no rolling off characteristics due to the electrical parasitics existing in the laser diodes. In particular, in the TM light injection scheme, no injection locking phenomena take place. A number of applications of TM light injection have been reported. In relation to these, determining the gain compression factors of laser diodes in the presence of TM light injection is essential. A new technique for determining these factors is presented. The technique is shown to be viable for measuring the gain compression of distributed feedback (DFB) lasers.<<ETX>>

The effect of reference's phase on radio-frequency holographic imaging

As electromagnetic waves provide a means of seeing through optically opaque dielectries, the technique of holographic imaging in the Fresnel zone furnishes a potential application to nondestructive testing. The technique also provides an ability of short-distance continuous wave (CW) imaging radar of moving targets. In this communication, the effect of the phase of the electronic reference on the imaging characteristics is experimentally confirmed. The effect of the references phase on the image quality is also examined.

Analysis of polarization bistability of phase-shifted DFB laser due to TM light injection

As a method of high-bit-rate optical processing, the TM light injection-induced optical polarization bistability using Fabry-Perot type laser diodes has been experimentally demonstrated and theoretically analyzed. In these studies, although switching times less than 1 ns both for switch-up and switch-down have been reported, both of the TE and TM outputs exhibit longitudinal multimode spectra. In practical processing systems, a dynamically stable operation of the polarization switching is considered to be essential. It is the purpose of this paper to present an analytical study of the TM light injection-induced polarization bistability using a lambda /4-shifted distributed feedback (DFB) laser model and to describe the detailed picture of the mechanism. >

A Simple EM Immune RF Probe Utilizing LED and Optical Fiber

An electromagnetic interference immune radio frequency probe composed of a loop and an LED linked with an optical fiber is presented and its characteristics are experimentally examined. In order to confirm its validity, some of the radio frequency fields measurements by the probe are also presented.

Sensitivity-enhancing scheme of a polarimetric heterodyne sensor using a birefringent fiber loop.

In order to improve the sensitivity of a fiber-optic polarimetric sensor, a new scheme utilizing a birefringent fiber loop with midloop frequency shifters is proposed. In this scheme, heterodyne signals with an integral multiple-phase sensitivity can be obtained in the frequency domain. The validity of the scheme is confirmed experimentally by a bulk-optic configuration. One-order-of-magnitude improvement in sensitivity without changing the dynamic range is expected from the calculation of the signal-to-noise ratio, even in the case of a 40% excess loss in the optical loop.