Nobunori Oura

Frequency Stabilization of AlGaAs Semiconductor Laser Based on the 85Rb-D2 Line

The frequency of an AlGaAs semiconductor laser was stabilized by using the linear absorption spectrum of the 85Rb-D2 line. By controlling the injection current, the frequency stability of 3.0×10-10σ1.4×10-12 was obtained for 10 msτ500 s. First observation of the saturated absorption spectrum of the 85Rb-D2 line is demonstrated, which can be used as a frequency reference to improve the frequency stability.

The refractive‐index distribution normal to the polished surface of fused quartz measured by ellipsometry

One of the dominant factors influencing the frequency aging of a crystal oscillator is the amount of surface irregularity left by polishing upon its crystal resonator. This paper deals with the refractive‐index distribution of fused quartz as a measure of polished layer depth. It is found that the refractive‐index distribution can be expressed by a combination of an exponential function and a linear function. The refractive index decreases exponentially from a surface value of 1.736 to a certain value at a depth of 50±10 A and from it decreases linearly to the bulk value of 1.460 at a depth of 2000±200 A.

Composite-type (87)Rb optical-pumping light source.

A (87)Rb hyperfine optical-pumping light source less than 4 cm long has been fabricated. Features of this new light source are: A 3-7-mm-long (85)Rb filter cell is attached to the front face of a cylindrical (87)Rb lamp with a diameter of 10mm, and both the lamp and the filter cell are operated at the same temperature of about 100 degrees C. A satisfactory spectral profile of D(1)-line output (lambda = 794.8 nm) has been observed by using a Fabry-Perot interferometer.

Effect of the worked layer in quartz-crystal plates on their frequency stabilities

Describes the direct measurement of the relation between the worked layers in quartz-crystal plates and their effect on the frequency stability. The rectangular fundamental 5-MHz AT-cut specimen plates lapped and polished with emery powder and cerium oxide, respectively, were placed in gap-type holders and connected with oscillator circuits, and their frequency stabilities were measured. The frequency stabilities are evaluated by the fractional frequency deviation to the nominal frequency ratio, power spectral density, and the Allan variance. The main results are: 1) The frequency drift due to the worked layer is dealt with as a relaxation process. It can be approximated by a sum of one to three terms of an exponential function. 2) The depth of the worked layer has a large effect not only on the long-term frequency stability but on the medium term in the Fourier frequency range of 10-3 to 10-7 Hz. 3) It does not have a dominant effect on the short-term stability with an averaging time of less than 10 s.

K-cut quartz SAW resonators for stable frequency sources

A new type of quartz SAW resonator for use as a stable frequency source has been developed. It was studied from the point of view of frequency instability caused by transient thermal behavior, and a new angle of cut named the K-cut for quartz SAW resonators was found. The static and dynamic frequency temperature coefficients are both zero at a room temperature. Taking into consideration the influence of the electrode-film thickness, the width modes of the waves, and power-flow angles, optimized resonators and oscillators were designed. These devices had frequency stability of 2/spl times/10/sup -10/ for the mean time of 0.01 s.

Analysis of the temperature dependence of 87 Rb lamp profiles

The temperature dependence of the spectral profile of the 87Rb D1 line (λ = 794.8 nm) observed by a Fabry-Perot interferometer has been discussed by considering the self-absorption mechanism in the lamp. The Rb lamp is assumed to be composed of two separated portions: One is a spherical core of emitting Rb atoms and the other is an outer layer of the same kind of absorbing atoms surrounding the core. The temperature dependence of the emitted light intensity, intensity difference between two hyperfine peaks, and asymmetry of the self-absorbed profiles are systematically explained in the temperature range of 75 to 125°C. The equivalent absorbing atom layer near the lamp surface is estimated to be 0.5 mm in this model.

Theoretical analysis of thermal frequency behavior of a SAW device being caused by laser beam irradiation and its dependence on angle of cut

The frequency excursion due to intermittent laser beam irradiation on the surface of a SAW device plate is analyzed by assuming that only one dimensional thermal stress in the propagation direction of SAW on the surface of the plate exists and a diameter of the beam is infinitesimal. As a result, specimen plates immune to transient environmental temperature change are made and their frequency trends better than those of the ST-cut plate are shown.<<ETX>>

Defects in Synthetic Quartz and the Q-Values of the -18.5° X-Cut Bar

-18.5° X-cut bar crystal blanks, 25.0×1.50×1.25 mm in size, were cut from different synthetic mother quartz. Defects in the bars were observed by light scattering tomography and X-ray traverse topography, Q-values were measured in the second overtone mode of 200 kHz in the air gap type holder and the maximum Q of 5.4×106 was obtained. Infrared absorption of the mother quartz, observed defects and the measured Q-values were discussed.

Generalized Equation for the Force-Frequency Characteristics of Circular Quartz Plates with Three-Point Support and Its Application to Supporting of an SC-Cut Plate

A generalized equation which expresses the force-frequency characteristics of a circular disk plate supported by three unsymmetrical points is derived from the concept of balance of applied forces and the superposition of virtual force pairs. Optimum supporting angles of an SC-cut plate, which is less immune to radially applied forces, are computed and the validity of the equation is confirmed with experiment. It is proposed that the most probable expansion coefficients of the force-frequency characteristics should be compiled from extensive experimental results.

Thermal Frequency Behavior in Contoured Quartz Crystal Plates Induced by Direct Irradiation of Laser Beam

Summary The oscillation frequency behavior of the quartz crystal plates is observed, while a laser beam as a kind of probe is irradiating different points of their principal surfaces. Such frequency behavior is characteristic to the respective angle of cut and is independent of the geometry and type of the electrode or support. There are three kinds of region on an AT-cut plate which show different types of thermal frequency behavior. The amounts of the frequency shifts in IT-cut and SC-cut plates are about 1/5 to 1/10 times those in AT-cut plate for the same irradiation power of the laser. The results suggest a possibility of compensation for the thermal frequency transient of a crystal unit by optimizing the electrode configuration and the reflectivity of the electrodes for the infrared rays.