Coupled mode analysis of light modulation in dielectric waveguides

A detailed analysis of electrooptic light modulation in optical waveguides is presented. Several important problems of a waveguide modulator, such as the difference of waveguide axes from crystalline electrooptic ones, the distribution of transverse and longitudinal field components of light modes, and the traveling-wave property of the modulating field, are discussed. The analysis is based on the coupled mode theory, regarding the modulation as the coupling among sidebands of unperturbed waveguide modes. The coupled mode equation is derived for the modulation in optical waveguides. It can be solved if the normal modes of the waveguide are given. Actually the equation is solved for the modulation in dielectric slab waveguides and the mechanism of modulation is discussed. The results of the analysis are applied to designing two types of waveguide modulators. In an example (10.6 μm modulator with a GaAs slab waveguide) a new efficient crystal orientation is found. The calculated phase retardation with this orientation is 0.13 rad/(V·cm) with a 1 μm thick slab. Another example of a 0.633 μm modulator using a LiTaO₃ crystal as a substrate is also described.     

A tunable waveguide CO2 laser with expanded tuning range

A method of expanding the tuning range of the CW CO₂ waveguide laser making use of a Fabry-Perot type light modulator is proposed. A preliminary experiment has been done to confirm the workability of the proposed scheme.     

Systematic Measurement of pd Breakup Cross Section Around Space Star

Space Star (SS) anomaly in nd breakup cross section was first reported in 1989 at E _n = 13 MeV (Strate et al. in Nucl Phys A 501:51, 1989), but its origin has not been found yet. In order to obtain suggestions for its origin, we made systematic measurements of pd breakup cross section around SS. In SS configuration, three outgoing nucleons form an equilateral triangle and the triangle is perpendicular to the beam axis. Necessity of the equilateral and perpendicular conditions of SS anomaly was investigated by systematic experiments. Also energy dependence of SS anomaly is being studied at energies from E _p = 7.5 to 13 MeV.     

A tunable waveguide CO2 laser using Fabry-Perot modulator and fox-smith type mode selector

A tunable waveguide CO₂ laser was constructed and tested. Efficient output was obtained over expanded tuning range making use of the coupling modulation through the F-P modulator. A fox-smith type mode selector was used to obtain the tuning range wider than the longitudinal mode spacing.A continuous tuning range of 2.2GHz was experimentally obtained.     

Über die Beziehungen zwischen den Faktorensystemen und der Normklassengruppe eines galoisschen Erweiterungskörpers

Ohne Zusammenfassung     

Modulation frequency dependence of actively mode-locked oscillation of A He-Ne 3.39 μm laser

The dependence of mode-locked oscillation of homogeneous lasers on the modulation frequency of locking signal is studied. An experiment using a He-Ne 3.39 μm laser and applying intracavity phase (FM) modulation was performed on the frequency range of 40 MHz to 1.20 GHz. The oscillation bandwidth was observed to be nearly proportion to $\text{√}\text{?}{}_{\mathrm{m}}$ and ?_m (?_m: modulation frequency) for the modulation frequency range of ?_m<Δ? and ?_m>Δ? (Δ?: linewidth), respectively. The possibility to generate ultra-short pulses by using larger modulation frequency than the linewidth is also discussed. For 1.20 GHz modulation frequency, the pulsewidth was estimated to be about 70 ps from the observed power spectrum, while the reciprocal of the linewidth was about 3 ns.     

Mode-locking of cw dye laser using externally modulated pumping laser

A new mode-locking method of tunable dye laser is described. This simple and practical method requires only an external intensity modulator to the pumping source. After the simple analytical considerations, the experimental work was done using an Ar laser pumped Rhodamin 6G dye laser and an acousto-optic modulator. As results, stable continuous trains of mode-locked pulses were obtained throughout in the ordinary lasing range 570–630 nm. The pulse width, estimated to be 30–50 ps by SHG autocorrelation measurements, is limited by the bandwidth of Lyot filter used. It is also shown experimentally that this method can be applicable for the suppression of the growth of double pulses in passive mode-locking with saturable absorber (DODCI).     

A Remark on Support of the Principal Function for Class A Operators

Let be an invertible class A operator such that . Then we show that , where gT is the principal function of T. Moreover, we show that if T is pure, then .     

Experimental Study of Space Star Anomaly in pd Breakup Around 10?MeV/A

Cross section of pd breakup at Star configuration (equilateral triangle) was systematically measured at E?=?9.5 and 13?MeV/A with varying an angle ?? between the Star plane and the beam axis. At 13?MeV/A, Star anomaly appears only around Space Star (?? =?90°) configuration. At 9.5?MeV/A, same feature was found in our experimental data at ?? =?0°?105°, but large difference of about ?25% at ???=?124°?180° was reported by K?ln group.