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In: Acta Sinica Quantum Optica, Shanghai Institute of Optics and Fine Mechanics, Vol. 22, No. 1 ( 2016), p. 74-80

Type of Medium: Online Resource

ISSN: 1007-6654

Uniform Title: 基于三波耦合波方程数值精确解分析外腔高效和频对腔模的影响

URL: Issue

URL: Journal

URL: Article

DOI: 10.3788/ASQO/2016/22/1

DOI: 10.3788/ASQO

DOI: 10.3788/ASQO20162201.0074

Language: English , Chinese

Publisher: Shanghai Institute of Optics and Fine Mechanics

Publication Date: 2016

In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 65, No. 7 ( 2016), p. 074202-

Abstract: In recent years, more than 90% of the signal laser power can be up-converted based on the high-efficiency double resonant external cavity sum-frequency generation (SFG), especially when the whole system runs under the undepleted pump approximation scheme. Therefore it is difficult to directly achieve an error signal with a high signal-to-noise ratio through the signal laser to lock its frequency to the cavity mode. In this paper a novel method, based on the frequency modulation of signal laser and demodulation of the SFG laser, is used to obtain the error signal to realize the cascade frequency locking between the two fundamental lasers and the external cavity. In this experiment, 1064 nm laser is the pump laser and 1583 nm laser is the signal laser. They are coupled into a ring cavity inside which a 5% MgO-doped PPLN (25 mm1 mm0.5 mm) is used to produce the SFG laser of 636 nm. When the pump laser is resonant with the external cavity, a circulating power of 14.3 W is obtained with its input power of 1.3 W. The reflectivity of the input coupling mirror of signal laser is 10% to restrain the impendence mismatch. The temperature of PPLN is set at 68.5 ℃ to reach the optimum SFG temperature. In order to keep the signal laser resonance inside the external cavity, one needs to lock its frequency to the cavity mode. A 28.5 kHz sinusoidal voltage is used to modulate the frequency of the signal laser so that the frequency of 636 nm laser is modulated simultaneously. Then 5% of the output 636 nm laser power is sent into a Si photodiode detector the signal of which is demodulated at the modulation frequency by a lock-in amplifier. Finally the demodulated signal is feedback to the frequency control port of signal laser. Under these conditions, 73% of 1583 nm signal laser power can be converted into 636 nm laser power when the incident power varies from 10 W to demodulation of the transmitted cavity mode of 1583 nm when the incident signal laser power is below 12 mW. When the signal laser power increases from 50 mW to 295 mW, the conversion efficiency linearly drops to 60%, which is mainly caused by depleting the 1064 nm pump laser power. Finally a 440 mW of 636 nm laser is generated with an incident signal laser power of 295 mW. This scheme can realize a high-efficiency SFG with a low input signal laser power or poor single-pass SFG efficiency.

Type of Medium: Online Resource

ISSN: 1000-3290 , 1000-3290

URL: Journal

URL: Article

DOI: 10.7498/aps

DOI: 10.7498/aps.65.074202

Language: Unknown

Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences

Publication Date: 2016

In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 65, No. 12 ( 2016), p. 128701-

Abstract: A continuous wave cavity ringdown spectroscopy based on a double-locking loop is proposed to improve the shortcoming of low acquisition rate of concentration in traditional scheme. A small portion of laser is separated to pass through a C2H2 reference cell, used to lock the laser frequency to the 1+3 band P(9)e absorption line of C2H2 at 6534.3634 cm-1 by the 1st harmonic demodulation of the frequency modulation spectroscopy. The remaining portion is incident on a high finesses cavity to observe the ringdown events. Meanwhile, the reflected light of cavity is used to extract the error signal to lock the laser based on the PDH frequency locking technique. As a consequence, the frequency drift of the laser and the jitter of the cavity length are improved, therefore a more relatively accuracy result is expected. The laser light is dual frequency modulated by a fiber coupled electro optic modulator (FEOM)in the above system. In order to optimize, to some extent, the asymmetry of the error signal caused by the residual amplitude modulation due to the inconsistency of the laser polarization direction with the extraordinary axis of the FEOM, the demodulation phase is adjusted carefully until the error signal is smoothed up and close to symmetry. Then, the effect of locking loop is examined. The frequency of laser, based on the measurement by a wavelength meter, is more stable and the relative frequency discrimination between the laser and the longitudinal mode of cavity is about 9.8 kHz. In addition, the PDH locking, ensuring the efficient coupling of the laser with the cavity, can gain a high acquisition rate of the concentration information. In order to obtain a complete ringdown event, the frequency of square wave to the fiber coupled acoustic optical modulator (FAOM) is limited to 30 kHz with the duty cycle of 85%, which is determined by the ringdown time and re-lock time. However, there exists a relatively large random noise in a series of ringdown time measurements of empty cavity, which is mainly caused by the errors of fitting and measurement. For the further improvement of the accuracy of experiment, an efficient digital filter, Kalman filter which can suppress the noise considerably at no expense of real-time capability, is used. The standard deviation of the ringdown time is reduced from 0.00333 to 0.00153. According to Allan variance analysis, the detection limit can reach 410-9 cm-1 for a 2 s integration time. Finally, the C2H2 gases with different concentrations from 100 ppb to 5 ppm are measured to demonstrate the linear response of this system.

Type of Medium: Online Resource

ISSN: 1000-3290 , 1000-3290

URL: Journal

URL: Article

DOI: 10.7498/aps

DOI: 10.7498/aps.65.128701

Language: Unknown

Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences

Publication Date: 2016

In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 65, No. 23 ( 2016), p. 234204-

Abstract: Fiber laser can be used for fiber optic communications,laser cutting,industrial manufacture,defense security and many other fields because of its advantages of narrow output linewidth,good reproducibility,etc.However,due to nonlinear and thermal effects,only a limited output power of a single fiber can be obtained with a sharp attenuation of the output beam quality,which obstructs the applications of fiber lasers.Therefore,the research of expanding the power of a fiber laser source while maintaining its beam quality by combining coherent beam has become a hot subject at present.In this field,the performance of phase control of coherent laser beams is a key factor to influence the efficiency of combination.The phase-controlling methods mainly include stochastic parallel gradient descent control algorithm, dithering,and heterodyne detection.In this paper,based on the active phase lock technology,the traditional heterodyne detection method is improved by the use of a fiber electro-optic phase modulator (EOM) rather than an acousto-optic frequency shifter (AOFS) to avoid the complex designs of the RF driver and circuit,which makes the overall experimental setup simple and stable.Moreover,in order to achieve a stable and wide correction range of phase locking,two servo paths are designed by use of piezoelectric transducer (PZT) and EOM1 to correct the optical phase differences.Firstly, a single-frequency narrow-width fiber laser with its central wavelength of 1531 nm is split by a beam splitter to generate a signal and a reference beam,respectively.The reference beam is phase modulated by another EOM2 with a 15 MHz signal.The phase error signal is obtained by demodulating the detected heterodyne signal at the modulation frequency. After that the error signal is divided into two parts,and sent to two PID servos to control PZT and EOM1,respectively. The PZT,used in the slow feedback loop,eliminates the laser phase error induced by the ambient temperature drift, while the EOM1,in the quick feedback loop,can eliminate the influence of high frequency noise.Two PID servos are carefully designed according to the measurements of the dynamic response of the PZT and EOM1.A stable feedback loop with a bandwidth of 220 kHz (limited by the bandwidth of PID controller) is obtained according to the measurement of its phase error signal spectrum,thus a tight lock is expected.As a consequence,the error of phase locking is less than 0.88°,which indicates that the phase control accuracy is λ/400.The long-term stability of the system is assessed by a 2 hour monitoring of the lock error signal.According to the analysis of Allan deviation,the best phase lock value of 0.006° can be obtained for an integration time of 160 s.The overall phase lock experimental setup is simple and easy to operate;moreover the phase lock can be further improved by optimizing the parameters of the PID controller.

Type of Medium: Online Resource

ISSN: 1000-3290 , 1000-3290

URL: Journal

URL: Article

DOI: 10.7498/aps

DOI: 10.7498/aps.65.234204

Language: Unknown

Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences

Publication Date: 2016

In: Acta Sinica Quantum Optica, Shanghai Institute of Optics and Fine Mechanics, Vol. 22, No. 1 ( 2016), p. 74-

Type of Medium: Online Resource

ISSN: 1007-6654

Uniform Title: Analyzation of the Influence of High Efficiency Sum Frequency Generation on the External Cavity Mode Based on the Numerical Exact Solution of TWEC

URL: Issue

URL: Journal

URL: Article

DOI: 10.3788/JQO/2016/22/1

DOI: 10.3788/JQO

DOI: 10.3788/jqo20162201.0011

Language: English , Chinese

Publisher: Shanghai Institute of Optics and Fine Mechanics

Publication Date: 2016

In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 67, No. 21 ( 2018), p. 213201-

Abstract: The transfer mechanism from the amplitude noise of the coupling light to the phase noise of the probe light in a Rydberg electromagnetic induced transparency effect derived from a ladder-type system including 6S1/2↔6P3/2↔62D5/2 of Cs atoms is demonstrated by using Mach-Zehnder interferometer and balanced homodyne detection technology. In our experiments, the transmission signal of 852 nm probe light is measured by scanning the coupling light frequency nearby the transition from 6P3/2 to 62D5/2 Rydberg state, while the frequency of the probe light is locked at the resonance transition of the 6S1/2↔6P3/2. The relative phase stability of two arms of Mach-Zehnder interferometer, which is constructed with the first order diffraction light of probe light through an acoustic-optic modulator, is accomplished by the controlled piezoelectric ceramic with the PID feedback loop. The interferences between the probe light and the reference light of Mach-Zehnder interferometer under the different relative phases are observed. The interference spectrum of probe light is in good agreement with the theoretical simulation result of the ladder-type three-level system. Therefore, we study the transfer characteristics from the frequency noise of coupling light to the phase noise of probe light when coupling light frequency resonance happens at the transition 6P3/2↔62D5/2. We find the significant suppression of the phase noise of probe light at the higher frequency noise. Moreover, we observe the characteristics of the phase noise of the probe light varying with the power of the coupling light under the different detuning degrees of coupling light. In the red detuning side, the transferred phase noise of probe light decreases with the increase of coupling light power, which is different significantly from the scenario under the blue detuning condition. The ions produced in the ionization process of Rydberg atoms will form the local electric field that would cause the energy level of Rydberg states to shift. The investigation of the noise transfer between the coupling light and probe light in the Rydberg electromagnetically induced transparency effect is important for understanding the coherence mechanism of ladder-type system and the some potential applications, such as in Rydberg-atom-based electric field metrology.

Type of Medium: Online Resource

ISSN: 1000-3290 , 1000-3290

URL: Journal

URL: Article

DOI: 10.7498/aps

DOI: 10.7498/aps.67.20181168

Language: Unknown

Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences

Publication Date: 2018

In: Acta Sinica Quantum Optica, Shanghai Institute of Optics and Fine Mechanics, Vol. 27, No. 1 ( 2021), p. 62-

Type of Medium: Online Resource

ISSN: 1007-6654

Uniform Title: Experimental Investigations on Preparation of Ultracold 85Rb133Cs Molecules in the Ground State Based on Resonant Coupling 33Σ+1 state

URL: Issue

URL: Journal

URL: Article

DOI: 10.3788/JQO/2021/27/1

DOI: 10.3788/JQO

DOI: 10.3788/jqo20212701.0501

Language: English , Chinese

Publisher: Shanghai Institute of Optics and Fine Mechanics

Publication Date: 2021

In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 70, No. 6 ( 2021), p. 063201-

Abstract: We present a high-sensitivity weak microwave measurement and communication technology by employing the Rydberg beat technique. The Rydberg cascade three-level system is composed of a cesium ground state 〈inline-formula〉〈tex-math id="M8"〉\begin{document}$6{\rm{S}}_{1/2}$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M8.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M8.png"/〉〈/alternatives〉〈/inline-formula〉, an excited state 〈inline-formula〉〈tex-math id="M9"〉\begin{document}$6{\rm{P}}_{3/2}$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M9.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M9.png"/〉〈/alternatives〉〈/inline-formula〉, and a Rydberg state 〈inline-formula〉〈tex-math id="M10"〉\begin{document}$n{\rm{D}}_{5/2}$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M10.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M10.png"/〉〈/alternatives〉〈/inline-formula〉 in a room-temperature cesium cell. A two-photon resonant Rydberg electromagnetic induced transparency (EIT) is used to optically detect the Rydberg level, in which a weak probe laser is locked at the resonant transition of 〈inline-formula〉〈tex-math id="M11"〉\begin{document}$|6{\rm{S}}_{1/2}\rangle \rightarrow |6{\rm{P}}_{3/2}\rangle$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M11.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M11.png"/〉〈/alternatives〉〈/inline-formula〉, and a strong coupling laser drives the transition of 〈inline-formula〉〈tex-math id="M12"〉\begin{document}$|6{\rm{P}}_{3/2}\rangle \rightarrow |n{\rm{D}}_{5/2}\rangle$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M12.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M12.png"/〉〈/alternatives〉〈/inline-formula〉. Both lasers are locked with a high-precision Fabry-Perot cavity. Two 〈i〉E〈/i〉-fields are incident into the vapor cell to interact with Rydberg atoms via a microwave horn, one is a strong microwave field with frequency 2.19 GHz, acting as a local field (〈inline-formula〉〈tex-math id="M13"〉\begin{document}$E_{{\rm{L}}}$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M13.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M13.png"/〉〈/alternatives〉〈/inline-formula〉) and resonantly coupling with two Rydberg energy levels, 〈inline-formula〉〈tex-math id="M14"〉\begin{document}$|68{\rm{D}}_{5/2}\rangle$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M14.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M14.png"/〉〈/alternatives〉〈/inline-formula〉 and 〈inline-formula〉〈tex-math id="M15"〉\begin{document}$|69{\rm{P}}_{3/2}\rangle$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M15.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M15.png"/〉〈/alternatives〉〈/inline-formula〉, and the other is a weak signal field (〈inline-formula〉〈tex-math id="M16"〉\begin{document}$E_{{\rm{S}}}$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M16.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M16.png"/〉〈/alternatives〉〈/inline-formula〉) with frequency difference 〈inline-formula〉〈tex-math id="M17"〉\begin{document}${\text{δ}} f$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M17.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M17.png"/〉〈/alternatives〉〈/inline-formula〉, interacting with the same Rydberg levels. The wave-absorbing material is placed around the vapor cell to reduce the reflection of microwave field. In the presence of the local field, the Rydberg atoms are employed as a microwave mixer for reading out the difference frequency 〈inline-formula〉〈tex-math id="M18"〉\begin{document}${\text{δ}}f$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M18.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M18.png"/〉〈/alternatives〉〈/inline-formula〉 oscillation signal, which is proportional to the amplitude of weak signal field. The minimum detectable field of 〈inline-formula〉〈tex-math id="M19"〉\begin{document}$E_{0} = 1.7$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M19.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M19.png"/〉〈/alternatives〉〈/inline-formula〉 μV/cm is obtained when the lock-in output reaches the base noise. We also measure the frequency resolution of the Rydberg mixer by changing the 〈inline-formula〉〈tex-math id="M20"〉\begin{document}${\text{δ}} f$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M20.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M20.png"/〉〈/alternatives〉〈/inline-formula〉 with fixed 〈inline-formula〉〈tex-math id="M21"〉\begin{document}$ f_{\rm ref} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M21.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20201401_M21.png"/〉〈/alternatives〉〈/inline-formula〉, thus achieving a frequency resolution better than 1 Hz. For neighboring fields with 1 Hz away from the signal field, an isolation of 60 dB is achieved. Furthermore, we use the Rydberg atom as an antenna to receive the baseband signals encoded into the weak microwave field, demonstrating that the receiver has a transmission bandwidth of about 200 MHz. The demonstration of sensitivity of Rydberg atoms to microwave field is particularly useful in many areas, such as quantum precise measurement and quantum communications. In general, this technique can be extended to the detection of electromagnetic radiation from the radio-frequency regime to the tera-hertz range and is feasible for fabricating a miniaturized devices, thereby providing us with a way to receive the information encoded in tera-hertz carriers in future work.

Type of Medium: Online Resource

ISSN: 1000-3290 , 1000-3290

URL: Journal

URL: Article

DOI: 10.7498/aps

DOI: 10.7498/aps.70.20201401

Language: Unknown

Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences

Publication Date: 2021

In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 66, No. 24 ( 2017), p. 243201-

Abstract: Chipless radio frequency identification tags have been widely used in many areas, such as vehicle recognition and identification of goods. Near-field measurement of a chipless radio frequency identification tag is important for offering the precise spatial information of the backscattered field of tag. In this paper, we demonstrate the angle discrimination of a line-shape chipless radio-frequency identification tag via the near-field measurements of scattered electric fields in two orthogonal directions. Two laser beams with different frequencies counter propagate and pass through a roomtemperature caesium vapor. A Rydberg ladder-type system is formed in the experiment, which includes three levels, namely 6S1/2, 6P3/2, 51D5/2. The electromagnetically induced transparency of transmission of probe light, which is locked to the transition of 6S1/2↔ 6P3/2, is observed when the frequency of coupling light varies nearby the transition of 6P3/2↔ 51D5/2. When the 5.366 GHz microwave electric field that is resonant with the transition between two adjacent Rydberg states 51D5/2↔ 52P3/2 is applied to the caesium vapor cell by using a standard-gain horn antenna, the transmission signal of probe laser splits into two peaks, which is known as Autler-Townes splitting. The splitting between the transmission peaks is proportional to the microwave electric field strength at the position of laser beam. The spatial distribution of backscattered microwave electric field of the chipless radio-frequency identification tag is obtained through varying the position of the laser beam. The spatial resolution of near-field measurement approximately equals λMW/12, where λMW is the wavelength of the measured microwave electric field. The distributions of the electric field strength in two orthogonal directions show the clarity difference while the angle of radio-frequency identification tag is changed. The scattered electric field strength of the identification tag is strongest when the angle of line-shape tag is the same as that of the polarization of the horn antenna. Moreover, the scattered field strength of identification tag in the incident field direction of the horn antenna increases as the measured position and the identification tag get closer to each other. The scattered electric field distributions in the vertical direction are almost constant at the different angles between the incident electric filed and identification tag. The fluctuation of spatial distribution of the scattered electric field strength is attributed to the Fabry-Pérot effect of microwave electric field in the vapor cell. And the geometry of vapor cell results in the minor asymmetric distribution of scattered field. The simulation results from the electromagnetic simulation software are accordant with the experimental results. The novel approach to near-field measurement of identification tag will contribute to studying and designing the chipless radio-frequency identification tag and complex circuits.

Type of Medium: Online Resource

ISSN: 1000-3290 , 1000-3290

URL: Journal

URL: Article

DOI: 10.7498/aps

DOI: 10.7498/aps.66.243201

Language: Unknown

Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences

Publication Date: 2017

In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 67, No. 10 ( 2018), p. 104207-

Abstract: Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is a powerful tool for trace gas detection, which is based on the combination of frequency modulation spectroscopy (FMS) for reduction of 1/f noise, especially residual intensity noise, and cavity enhanced absorption spectroscopy (CEAS) for prolonging the interaction length between the laser and the targeted gas. Because of the locking of modulation frequency in FMS to the free spectral range (FSR) of the cavity, NICE-OHMS is immune to the frequency-to-amplitude noise, which is a main limitation to CEAS. Moreover, due to the building of high power inside the cavity, NICE-OHMS can easily saturate the molecular absorption thus obtain sub-Doppler spectroscopy, which possess a high resolution and odd symmetry, and thus can act as a frequency discriminator for the locking of the laser frequency to the transition center. In this paper, a fiber laser based NICE-OHMS system is established and the laser frequency is locked to the sub-Doppler absorption line of NH3 by sub-Doppler NICE-OHMS. To avoid the complex design of high-Q-factor bandpass filter at radio frequency, the frequency νpdh, used for Pound-Drever-Hall (PDH) locking, is generated by the beat frequencies νfsr and νdvb, which are used for NICE-OHMS signal and DeVoe-Brewer (DVB) locking, respectively. The performances of PDH and DVB locking are analysed by the frequency distribution deduced from the error signals, which result in frequency deviations of 4.3 kHz and 0.38 kHz, respectively. Then, the CEAS signal and NICE-OHMS signal in the dispersive phase for the measurement of NH3 at 1.53 μm under 70 mTorr are obtained, which show signal-to-noise ratios of 3.3 dB and 45.5 dB, respectively. Due to the high power built in the cavity, the sub-Doppler structure in the NICE-OHMS signal is obtained in the center of the absorption tansition with a satruation degree of 0.22, which is evaluated by the amplitude ratio between sub-Doppler and Doppler-broadened signals. The linewidth (full width at half maximum) of the sub-Doppler signal of 2.05 MHz is obtained, which is calibrated by the time interval between carrier and sideband. The free-running drift of the laser frequency is estimated by the NICE-OHMS signal and results in 50 MHz over 3 h. While, with locking, the relative deviation of the laser frequency is reduced to 16.3 kHz. In order to evaluate the long term stability of the system, the frequency deviation over 3 h is measured. The Allen deviation analysis shows that the white noise is the main noise of the system in the integration time shorter than 10 s. And the frequency stability can reach to 1.6×10-12 in an integration time of 136 s.

Type of Medium: Online Resource

ISSN: 1000-3290 , 1000-3290

URL: Journal

URL: Article

DOI: 10.7498/aps

DOI: 10.7498/aps.67.20172541

Language: Unknown

Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences

Publication Date: 2018