# Portable THz Frequency Standard using Difference-Frequency Generation of Acetylene-Stabilized Telecom Diode Lasers

28 Aug 2022-pp 1-2

TL;DR: In this article , a portable THz frequency standard was developed based on difference-frequency generation (DFG) of two telecom lasers in a uni-traveling-carrier photodiode (UTC-PD).

Abstract: We have developed a portable THz frequency standard. It is based on difference-frequency generation (DFG) of two telecom lasers in a uni-traveling-carrier photodiode (UTC-PD). Both lasers were simultaneously stabilized to acetylene $(^{13}\mathrm{C}_{2}\mathrm{H}_{2})$ transitions by modulation transfer spectroscopy using one reference gas cell. The fractional instability of the THz standard at 288GHz was attained to be $1\times ^{10-8}$ over 400s averaging time. This THz standard serves as a new wavelength reference for THz spectroscopy equipments and consequently improves their measurement accuracy.

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TL;DR: In this article, the frequency of a terahertz quantum-cascade laser is stabilized to the absorption line of methanol gas at a frequency of 2.55 THz.

Abstract: The frequency of a terahertz quantum-cascade laser is stabilized to the absorption line of methanol gas at a frequency of 2.55 THz. The method is based on frequency modulation of the laser emission across the absorption line. The resulting derivativelike signal is used as an error signal for a control loop that keeps the laser frequency at maximum absorption. The unstabilized laser that is operated in a pulse tube cooler has frequency fluctuations of 15 MHz, which are reduced to 300 kHz with the control loop in action. The line shape of the locked signal is Gaussian.

69 citations

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TL;DR: In this paper, a pair of 1.5 μm semiconductor laser frequency standards have been developed for optical telecommunications use, stabilised to Doppler-free transitions of the ν1+ ν3 and ν 1 + ν2 + λ 4 + ξ 5 combination bands of 13C2H2.

Abstract: A pair of 1.5 μm semiconductor laser frequency standards have been developed for optical telecommunications use, stabilised to Doppler-free transitions of the ν1 + ν3 and ν1 + ν2 + ν4 + ν5 combination bands of 13C2H2. The Allan deviation σ/f for a laser locked to line P(10) of the former band follows a slope of 1.6 × 10−12τ−1/2, reaching a minimum of 5.7 × 10−14 at τ = 4000 s. The absolute frequencies of 61 lines of the ν1 + ν3 band and 43 lines of the ν1 + ν2 + ν4 + ν5 band, covering the spectral region 1520 nm to 1552 nm, have been measured by use of a combined frequency chain and femtosecond comb, together with a passive optical frequency comb generator. The mean uncertainties for the line frequencies within each band are 1.4 kHz for the ν1 + ν3 band and 1.9 kHz for the ν1 + ν2 + ν4 + ν5 band, representing improvements on the precision of previously published data by factors of 100 and 104, respectively. Improved values of the rotational constant B″ and centrifugal distortion coefficients D″, H″ and L″ of the vibrational ground state are presented.

56 citations

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01 Jul 2018TL;DR: In this paper, the sub-terahertz rotational transitions of polar gaseous molecules are used as frequency bases to create low-cost, low-power miniaturized clocks.

Abstract: Mobile electronic devices require stable, portable and energy-efficient frequency references (or clocks). However, current approaches using quartz-crystal and microelectromechanical oscillators suffer from frequency drift. Recent advances in chip-scale atomic clocks, which probe the hyperfine transitions of evaporated alkali atoms, have led to devices that can overcome this issue, but their complex construction, cost and power consumption limit their broader deployment. Here we show that sub-terahertz rotational transitions of polar gaseous molecules can be used as frequency bases to create low-cost, low-power miniaturized clocks. We report two molecular clocks probing carbonyl sulfide (16O12C32S), which are based on laboratory-scale instruments and complementary metal–oxide–semiconductor chips. Compared with chip-scale atomic clocks, our approach is less sensitive to external influences and offers faster frequency error compensation, and, by eliminating the need for alkali metal evaporation, it offers faster start-up times and lower power consumption. Our work demonstrates the feasibility of monolithic integration of atomic-clock-grade frequency references in mainstream silicon-chip systems. The sub-terahertz rotational transitions of polar molecules can be used as frequency bases to create low-cost, low-power miniaturized clocks.

35 citations

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TL;DR: In this article, the authors reported frequency locking of two 3.5-THz third-order distributed feedback (DFB) quantum cascade lasers (QCLs) by using methanol molecular absorption lines, a proportional-integral-derivative controller, and a NbN bolometer.

Abstract: We report frequency locking of two 3.5-THz third-order distributed feedback (DFB) quantum cascade lasers (QCLs) by using methanol molecular absorption lines, a proportional-integral-derivative controller, and a NbN bolometer. We show that the free-running linewidths of the QCLs are dependent on the electrical and temperature tuning coefficients. For both lasers, the frequency locking induces a similar linewidth reduction factor, whereby the narrowest locked linewidth is below 18 kHz with a Gaussian-like shape. The linewidth reduction factor and the ultimate linewidth correspond to the measured frequency noise power spectral density.

31 citations