Analysis on high-resolution spectrum of the S1-S0 transition of free-base phthalocyanine.

A high-resolution absorption spectrum of the S1-S0 transition of free-base phthalocyanine was observed and analyzed with improved reliability. The spectrum, with a partially resolved rotational structure, was obtained by using the buffer-gas cooling technique and a single-mode tunable laser. Our new analysis reveals that the S1←S0000 band belongs to the a-type transition, where the electronic transition moment aligns parallel to the NH-HN direction, allowing the assignment of the S1 state to 1B3u.

Doppler-free Spectroscopy of Buffer-Gas-Cooled Calcium Monohydroxide.

In this study, we report the Doppler-free spectra of buffer-gas-cooled CaOH. We observed five Doppler-free spectra containing low- Q and R transitions, which were only partially resolved by previous Doppler-limited spectroscopies. The spectra frequencies were corrected using the Doppler-free spectra of iodine molecules; accordingly, the uncertainty was estimated to be below 10 MHz.

High-resolution spectroscopy of buffer-gas-cooled phthalocyanine.

For over five decades, studies in the field of chemical physics and physical chemistry have primarily aimed to understand the quantum properties of molecules. However, high-resolution rovibronic spectroscopy has been limited to relatively small and simple systems because translationally and rotationally cold samples have not been prepared in sufficiently large quantities for large and complex systems. In this study, we present high-resolution rovibronic spectroscopy results for large gas-phase molecules, namely, free-base phthalocya-nine (FBPc).

Mid-infrared dual-comb spectroscopy with electro-optic modulators.

Absorption spectroscopy of fundamental ro-vibrational transitions in the mid-infrared region provides a powerful tool for studying the structure and dynamics of molecules in the gas phase and for sensitive and quantitative gas sensing. Laser frequency combs permit novel approaches to perform broadband molecular spectroscopy. Multiplex dual-comb spectroscopy without moving parts can achieve particularly high speed, sensitivity and resolution.

Phase-stabilized 100 mW frequency comb near 10 μm.

Long-wavelength mid-infrared (MIR) frequency combs with high power and flexible tunability are highly desired for molecular spectroscopy, including investigation of large molecules such as C. We present a high power, phase-stabilized frequency comb near 10 μm, generated by a synchronously pumped, singly resonant optical parametric oscillator (OPO) based on AgGaSe. The OPO can be continuously tuned from 8.

Ortho-Para-Dependent Pressure Effects Observed in the Near Infrared Band of Acetylene by Dual-Comb Spectroscopy.

We demonstrate that dual-comb spectroscopy, which allows one to record broadband spectra with high frequency accuracy in a relatively short time, provides a real advantage for the observation of pressure-broadening and pressure-shift effects. We illustrate this with the ν_{1}+ν_{3} vibration band of ^{12}C_{2}H_{2}. We observe transitions from P(26) to R(29), which extend over a 3.

Generation of a frequency comb spanning more than 3.6 octaves from ultraviolet to mid infrared.

We have observed an ultra-broadband frequency comb with a wavelength range of at least 0.35 to 4.4 μm in a ridge-waveguide-type periodically poled lithium niobate device.

Sub-Doppler resolution mid-infrared spectroscopy using a difference-frequency-generation source spectrally narrowed by laser linewidth transfer.

The spectral linewidth of a 3.28 μm difference-frequency-generation source has been reduced to 3.5 kHz using a laser linewidth transfer technique [Opt.

Design of cavity-enhanced absorption cell for reducing transit-time broadening.

To reduce the linewidth of Lamb dips, we introduce a cavity-enhanced absorption cell (CEAC) coupled with a Gaussian beam with a 1.9-mm 1/e(2) radius at the beam waist for the reduction of transit-time broadening. We state that transit-time broadening depends only on the beam radius at the beam waist.

A novel frequency control scheme for comb-referenced sensitive difference-frequency-generation spectroscopy.

We present a novel scheme of frequency scan and wavelength modulation of a difference-frequency-generation source for comb-referenced sensitive spectroscopy. While the pump and signal frequencies are phase-locked to an optical frequency comb (OFC), the offset frequency between the signal wave and the nearest comb tooth is modulated to apply a wavelength-modulation technique, and the idler wave frequency is repeatedly swept for signal accumulation by changing the repetition frequency of the OFC. The spectrometer is applied to absolute frequency measurement of weak hyperfine-resolved rovibration transitions of the ν(1) band of CH(3)I, and the uncertainty in frequency determination is reduced by one order of magnitude in compared with that of the previous work published in Optics Express 20, 9178-9186 (2012).

Spectroscopy of 171Yb in an optical lattice based on laser linewidth transfer using a narrow linewidth frequency comb.

We propose a novel, high-performance, and practical laser source system for optical clocks. The laser linewidth of a fiber-based frequency comb is reduced by phase locking a comb mode to an ultrastable master laser at 1064 nm with a broad servo bandwidth. A slave laser at 578 nm is successively phase locked to a comb mode at 578 nm with a broad servo bandwidth without any pre-stabilization.

Narrow linewidth comb realized with a mode-locked fiber laser using an intra-cavity waveguide electro-optic modulator for high-speed control.

We have developed an optical frequency comb using a mode-locked fiber ring laser with an intra-cavity waveguide electro-optic modulator controlling the optical length in the laser cavity. The mode-locking is achieved with a simple ring configuration and a nonlinear polarization rotation mechanism. The beat note between the laser and a reference laser and the carrier envelope offset frequency of the comb were simultaneously phase locked with servo bandwidths of 1.

Absolute frequency list of the ν3-band transitions of methane at a relative uncertainty level of 10(-11).

We determine the absolute frequencies of 56 rotation-vibration transitions of the ν(3) band of CH(4) from 88.2 to 90.5 THz with a typical uncertainty of 2 kHz corresponding to a relative uncertainty of 2.