Yukito Matsuo

High‐repetition‐rate optical pulse generator using a Fabry‐Perot electro‐optic modulator

A high‐repetition‐rate optical pulse generator which employs a Fabry‐Perot electro‐optic modulator as the output coupler of a laser resonator was constructed. Using this generator with a He–Ne 6328‐A laser tube, 21‐psec optical pulses at a repetition rate of 2.7 × 109 pps were experimentally obtained with an average power level of 0.5 mW. In addition, it is demonstrated that the width of the pulses obtained from this generator can be narrowed without regard to the gain‐linewidth limitation. This kind of pulse generator may be particularly useful for obtaining short optical pulses from low‐gain gas lasers, and it is possible to obtain 1010‐pps picosecond pulses from a He–Ne 6328‐A laser.

An intensity/phase autocorrelator for the use of ultrashort optical pulse measurements

Abstract An autocorrelator capable of providing both the phase and the intensity correlations within a single run is described. In this autocorrelator, a mechanical scan scheme was employed, wherein an alternative repetition of slow and fast scans was used for separating the intensity and the phase correlations. The constructed autocorrelator was sufficiently stable to retain the phase correlation component. The simultaneous measurement of the phase and the intensity correlation can provide the possibility to determine quickly the existence of a transform-limited relation in an observed pulse.

Magnetostatic surface wave propagation on a periodic YIG film layer

The filter characteristics of a magnetostatic surface wave propagating in a layered YIG film corrugated on one layer and noncorrugated on the other are described. The effect of the saturation magnetization of a noncorrugated layer on the filter is analytically evaluated by solving the exact dispersion relation. Also, the magnetic loss effect on the filter is considered. It is found that the Q value of the filter in our new model is generally twice as large as that of contemporary periodic YIG film filters.

Electrooptic-distributed Bragg-reflection modulators for integrated optics

The electrooptic-distributed Bragg-reflection modulators having periodically corrugated surfaces are proposed. Principles of distributed-feedback (DFB) and distributed Bragg-reflector (DBR) modulators are outlined and discussed. Calculations for the power per unit bandwidth indicate that the DBR modulator is much more effective than the DFB modulator.

Magnetostatic Surface Waves in Ferrite Slab Adjacent to Semiconductor (Short Papers)

Magnetostatic surface waves propagating along the ferrite slab adjacent to a semiconductor are discussed in this paper. Our numerical results indicate that the conductivity of the semiconductor plays an important role in the determination of the dispersion relation in the case of nondrifting carriers. The backward wave appears for a finite value of the conductivity.

Azimuthally Dependent Magnetostatic Modes In The Cylindrical Ferrites (Correspondence)

The azimuthally dependent magnetostatic modes have been investigated for two cases: 1) a hollow ferrite pipe is enclosed in a perfectly conducting wall; and 2) a ferrite rod is located at the center of a round waveguide, partially filling the cross section. Our analysis shows that the presence of the dielectric medium has an important role in the determination of the upper bound frequency and the cutoff wave number of the magnetostatic surface modes.

Field effect semiconductor lasers

A new semiconductor laser, the field-effect semiconductor (FES) laser, in which the both sides of the active region are surrounded by the burying layers with the reverse-biased p-n junctions is proposed. The proposed FES laser is a Q -switching device based on the direct control of laser beam intensity by the internal loss modulation through the field effect. The structure design and the operating principles of the device are discussed. Numerical solution shows that a pulsewidth shorter than 30 ps can be obtained.

Amplification of magnetostatic surface waves in a layered structure consisting of metals, dielectrics, a semiconductor, and YIG

The amplifying characteristics of magnetostatic surface waves (MSSW) propagating in a layered structure consisting of metal plates, dielectrics, a semiconductor, and a YIG slab are given. The dispersion relation of the system is derived under the condition of magnetostatic approximation. From the results of computer solution for the dispersion equation, we conclude that a growing MSSW occurs only when the carrier drift velocity is greater than phase velocity of the MSSW. The effect of YIG loss on the wave instability is considered. Also, the influence of a gap between the semiconductor and the YIG slab on the amplifier is discussed.

Ultrashort pulses from a cw dye laser using passive-active mode locking technique

Abstract For the purpose of improving the utilization efficiency of the gain bandwidth of active media and generating stable ultrashort light pulses, a passive-active mode locking technique has been applied to a cw Rhodamine 6G dye laser. A sufficient ability of this technique for the elimination of the multiple-pulse operation of the mode locking at a higher pumping level and a longer resonator length has been proved. Observed pulse-width by the SHG autocorrelation technique is 1.4 ps with assuming a sech 2 pulse profile.

Energy Analysis for the Amplification Phenomena of Magnetostatic Surface Waves in a YIG-Semiconductor Coupled System

Amplification phenomena of magnetostatic surface wages (MSSWs) in a ferrite-semiconductor system are analyzed in detail for the first time from an energy view point. For the interactions between MSSWs containing a backward branch and carrier streams in a semiconductor, the dispersion relations are given and the energy conservation law is applied to the system. The results in terms of energy quantities are found to be consistent with the solutions of the dispersion equation and well explain the amplifying mechanism microscopically. We conclude that this kind of interaction is a negative energy dissipation type of instability.