Atsuo Morinaga

Optical frequency standards

Frequency standards operating in the optical range promise very low frequency uncertainties due to the high spectral resolution and the small sensitivity to external fields. Basic ideas and concepts for the development of optical frequency standards are reviewed with emphasis to laser cooling and ion storing. Utilizing cooled absorbers, potential fractional frequency uncertainties below 10/sup -15/ are envisaged. Phase-coherent frequency measurements of laser radiation at lambda =3.39 mu m and a concept for an extension towards the visible range are discussed. A Ca optical frequency stabilized to the intercombination line ( lambda approximately=657 nm) utilizing Ramsey excitation of a single recoil component is described. The present estimated fractional uncertainty to find the Ca line center is about 2.3*10/sup -12/. It can probably be improved significantly by reducing phase shifts of the Ramsey excitation and by atomic beam cooling. >

Nonlinear optical properties of tin-phthalocyanine thin films

Abstract The nonlinear optical properties of evaporated tin–phthalocyanine thin films were investigated through absorption measurement, atomic force microscopy, and transmissivity measurement using a z-scan method. The pyramidal molecules fabricated by vacuum evaporation while applying a high electric field parallel to the substrate had large third-order nonlinear susceptibility of 3.8×10−8 esu.

Hyperfine Structure of Low-Lying Vibrational Levels in the B Electronic State of Molecular Iodine

The hyperfine structures of the weak lines R(69) in the 3–4 band and P(84) in the 5–5 band of the B ← X electronic transition in molecular 127I2 at λ = 657 nm have been detected by the method of FM saturation spectroscopy. Frequency separations between the hyperfine components were measured, and the hyperfine coupling constants for the electric quadrupole interaction and the magnetic spin-rotation interaction were determined. For low vibrational levels of the B state, eQqB depends linearly on the vibrational energy of the level υB according to eQqB (MHz) = −0.01721G(υB) (cm−1) −484.89. ΔC is almost constant for υB values smaller than 6.

Penetration Effects for Internal Conversions in the Odd-Mass Isotopes of La and Cs

Penetration parameters λ are determined by using internal conversion intensities and coefficients for low energy hindered M1 transitions of 131 Cs, 135 La, 137 La and 139 La together with E2/M1 mixing ratios δ 2 . The results are; λ(86.9, 135 La)=14.5±5.5, λ(10.5, 137 La)=10±5, λ(166, 139 La)=3.6±1.8 and λ(92.3, 131 Cs)=4±4, where numbers in parentheses are transition energies in keV.

Frequency locking a dye laser to the central optical Ramsey fringe in a Ca atomic beam and wavelength measurement

The frequency of a dye laser is stabilized to the 3P1–1S0 intercombination line of 40Ca through use of the first-derivative signal of the Ramsey fringes detected in a Ca atomic beam. The long-term stability of the frequency of the Ca-stabilized dye laser is estimated to be a few kilohertz from the servo error signal. The wavelength of the Ca-stabilized dye-laser beam is measured by comparison with that for an I2-stabilized He–Ne laser, which is one of the current wavelength standards. The measured wavelength is evaluated to be 657.4594396 nm with an uncertainty of better than 1 × 10−9.

Sub-hertz-linewidth diode laser stabilized to an ultralow-drift high-finesse optical cavity

An external cavity diode laser stabilized to a high-finesse rigid cavity made of ultralow-expansion (ULE) glass maintained at a zero-crossing temperature of −3.3 °C showed a linear frequency drift of 25 mHz/s, which was the lowest ever reported with ULE glass. The linewidth of the beat note between two independent laser systems stabilized to independent ULE glass cavities was narrower than 1 Hz, and the Allan deviation of the beat note around 1 s of averaging time was close to the Brownian thermomechanical noise limit.

Molecular Size Dependence in Third Order Susceptibility of Evaporated Tin-Phthalocyanine Thin Film

Abstract Molecular size dependence in third order optical susceptibility χ(3) for evaporated tin-phthalocyanine thin film was examined by methods of a scanning electron microscope technique (SEM) and an optical third harmonic generation (THG) Maker-fringe technique. Evaporated molecular size influenced greatly the values of χ(3). The thicker molecular size grew, the greater values of χ(3) were. The values were greater with increasing the order orientation OA= A⊥/(A⊥+AII), whose preferential direction was parallel to the major axis of microcrystals.

Accuracy and stability of a calcium-stabilized dye laser by means of the optical Ramsey resonance

The frequency of a dye laser was stabilized to the optical Ramsey resonance of the Ca intercombination line (/sup 1/S/sub 0/-/sup 3/P/sub 1/ at 657.46 nm), with a quality factor of 10/sup 10/. The beat frequency between two laser beams, which are independently stabilized to Ramsey resonances of two different atomic beams, is measured in order to evaluate the performance of the Ca-stabilized dye laser. A frequency stability of 2*10/sup -12//sub tau //sup -1/2/ is obtained for 1 >

A dye laser spectrometer with an external iodine cell designed for optical Ramsey-Fringe spectroscopy in a Ca atomic beam

A novel dye laser spectrometer stabilized to a hyperfine component of molecular iodine as a frequency reference was developed for observing optical Ramsey fringes in a Ca atomic beam. The resolution of the spectrometer was less than 1 kHz and the uncertainty of the absolute frequency was within 20 kHz. By using this spectrometer, Ramsey fringes with a width of 10 kHz and a signal-to-noise ratio of 200 were obtained with an integration time of 5 ms. The frequency separation between lines of Ca (1S0-3P1) and I2. (g, 3–4, R(67)) was measured to be 191.48±0.02 MHz.

Frequency stabilization of a dye laser to a reference cavity with sub-Hertz relative linewidth

We reduced the frequency fluctuation of a cw single frequency dye laser to the shot-noise limit at the Fourier frequency between 7 kHz and 20 kHz by the phase modulation technique. From the spectral density and the distribution of the instantaneous amplitude of the error signal, the relative linewidth of a dye laser to the reference cavity was estimated to be sub-Hz.