March 2024
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24 Reads
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Publications (182)
March 2024
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27 Reads
February 2024
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136 Reads
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2 Citations
We demonstrated an ultrafast time-resolved measurement method operating at the single-photon level and employing a two-color comb-based asynchronous optical sampling (ASOPS) setup. We harnessed the two-color ASOPS photon counting approach to achieve long-term averaging of the ultralow intensity signal with a synchronized optical trigger signal, which minimizes residual timing jitter between the two combs. A pulse-width limited picosecond cross-correlation signal was successfully obtained with a power level of <1 photon/pulse. This approach enables the thorough study of ultrafast time-resolved detection of entangled photon pairs, quantum mechanical correlations in the time-frequency domain and finds wide use in optical quantum technology.
![The performance of RAM suppression observed via (left) in-loop and (right) out-of-loop detectors for no RAM suppression (RS), 20 dB RS, 40 dB RS, 60 dB RS, and 66 dB RS and their noise floor and the calculated shot noise floor [for (left) only] normalized against the respective carrier powers. The RBW was 10 Hz, the number of averages was 20 for all plots, and the laser was locked to the two-photon transition for all plots except for PD noise and shot noise floors. Both PD noise floors were taken when the modulation signal was on but the fiber amplifier off, indicating no RF crosstalk between the modulation output and the monitors.](https://www.researchgate.net/publication/378340549/figure/fig3/AS:11431281289991091@1731473965946/The-performance-of-RAM-suppression-observed-via-left-in-loop-and-right-out-of-loop_Q320.jpg)
February 2024
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23 Reads
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1 Citation
We designed a field-programmable gate array (FPGA) fabric to provide phase modulation techniques to lock lasers to optical frequency references. The method incorporates an active residual amplitude modulation (RAM) suppression scheme that relies on complex modulation. All the required servos to construct an optical atomic clock are incorporated into the same low-cost, commercial FPGA chip. We demonstrate a reliable, long-term RAM suppression of 60 dB with the remaining RAM level at −100 dBc and an improved stability of three decades when applied on a two-photon rubidium clock.
January 2024
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134 Reads
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5 Citations
Optical frequency combs (OFCs) have become essential tools in a wide range of metrological and scientific research fields. However, in the reported literature, OFCs that cover the visible spectral range have a limited bandwidth and pulse energy. These drawbacks limit their potential applications, such as high-signal-to-noise ratio spectroscopic measurements. In this work, we demonstrate a broadband, high-power optical frequency comb covering the visible to near-infrared range (550 nm to 900 nm) with a high average power of approximately 300 mW. This is accomplished by the power scaling of optical pulses from a fully stabilized Er:fiber comb, coherent spectral broadening and finally the utilization of a PPLN’s χ⁽²⁾ nonlinearity. The broadband, high-power, fully stabilized visible OFCs showcased in this work offer reliable laser sources for high-precision spectroscopic measurements, imaging, and comparisons of optical clocks.
January 2024
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3 Reads
We demonstrate the generation of a broadband high-power dual-comb source spanning from visible to NIR range based on nonlinear broadening and wavelength conversion of an Er fiber comb. Preliminary dual-comb measurements successfully retrieved the broad visible spectrum.
March 2023
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7 Reads
February 2023
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85 Reads
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11 Citations
Laser & Photonics Review
Optical frequency combs are essential tools for precision metrology experiments ranging in application from remote spectroscopic sensing of trace gases to the characterization and comparison of optical atomic clocks for precision time‐keeping and searches for physics beyond the standard model. Presented here is a description of the architecture and a full characterization of a telecom‐band, self‐modelocking frequency comb based on a free‐space laser with an Er/Yb co‐doped glass gain medium. The laser provides a robust and cost‐effective alternative to Er:fibre laser based frequency combs, while offering stability and noise performance similar to Ti:sapphire laser systems. Finally, the utility of the Er/Yb:glass frequency comb is demonstrated in high‐stability frequency synthesis using two ultra‐stable optical references at 1157 nm and 1070 nm and in low‐noise photonic microwave generation by dividing these references to the microwave domain. Optical frequency combs are essential tools for precision metrology, such as in optical atomic clock experiments and ultra‐low noise microwave generation. The Er/Yb:glass free‐space modelocked laser is a low‐cost telecom wavelength laser, which combines the versatility and robustness of user‐friendly Er:fibre modelocked lasers with the excellent performance of Ti:sapphire modelocked lasers.
November 2022
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23 Reads
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4 Citations
Physical Review A
We propose a scheme for interrogating a warm rubidium vapor using two different clock lasers. Performance wise, this approach is distinctly different from the recently proposed two-color two-photon rubidium clocks as our scheme does not trade off the ac Stark suppression against an increased sensitivity to the cell temperature or pressure. Instead, our approach compensates both the ac Stark shift and the temperature and pressure-induced frequency shifts. The proposed scheme also makes use of the modulation transfer technique, which enables a two orders of magnitude increase in the signal-to-noise ratio compared to traditional clocks that rely on fluorescence measurements.
August 2022
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130 Reads
Optical frequency combs are an essential tool for precision metrology experiments ranging in application from remote spectroscopic sensing of trace gases to the characterization and comparison of optical atomic clocks for precision time-keeping and searches for physics beyond the standard model. Here we describe the architecture and fully characterize a telecom-band, self-modelocking frequency comb based on a free-space laser with an Er/Yb co-doped glass gain medium. The laser provides a robust and cost-effective alternative to Er:fiber laser based frequency combs, while offering stability and noise performance similar to Ti:sapphire laser systems. Finally, we demonstrate the Er/Yb:glass frequency comb's utility in high-stability frequency synthesis using two ultra-stable optical references at 1157 nm and 1070 nm and in low-noise photonic microwave generation by dividing these references to the microwave domain.
Citations (55)
... In contrast, diode lasers typically need complex stabilization methods, such as feedback from high-Q cavities or locking to external references, to achieve the spectral purity of fiber lasers [10][11][12]. With free-running linewidth in the kHz range, single-frequency fiber lasers can be used to trap and cool atoms in magneto-optical traps (MOTs) without conventional high-finesse locking or noise reduction schemes, and have been implemented in atomic clock systems based on Sr, Yb, and Rb to address the optical transitions required for their operation [13][14][15]. Here, we develop a modular system that combines custom Tm-doped fiber lasers and amplifiers with non-linear frequency conversion processes to deliver enough power at 689 nm and 698 nm. ...
- Citing Article
- Publisher preview available
February 2024
... In these systems, both the temporal resolution and dead time is influenced by the performance of the Si APDs. On the other hand, employing a femtosecond pulse laser as the pump light has enabled femtosecond order temporal resolution [20][21][22][23][24]. Kuzucu et al. [25,26] measured a temporal waveform correlation of photon pairs using a UCSPD with a 1-mm-long periodically poled Mg-doped stoichiometric lithium tantalate (PPMg:SLT) crystal and a femtosecond pulse laser. ...
- Citing Article
- Full-text available
February 2024
... Optical frequency comb [19][20][21][22][23][24] stands out as a promising solution to resolve this problem. In recent years, the rapid development of fiber comb technology has led to the development of compact and less complex fiber comb systems, which are highly suitable for high-resolution strain sensing applications [6,7,25]. ...
- Citing Article
- Publisher preview available
January 2024
... We generated the two ultrastable 10 GHz signals for our synthesizer using two optical frequency combs to divide down the optical references. One comb was based on a Ti:Sapphire mode-locked laser producing pulses at a rate of 1 GHz 5 , and the other comb was based on an Er/Yb:glass mode-locked laser with a 500 MHz repetition frequency ( f rep ) 11 . Both combs were fully stabilized with one comb tooth phase-locked to the optical reference laser, v opt , while simultaneously stabilizing the carrier offset frequency, f o , detected via a f-to-2f interferometer. ...
- Citing Article
February 2023
Laser & Photonics Review
... This allows for approximately tenfold less optical power and ten-fold lower rubidium vapor density needed to achieve fractional frequency stability comparable to the single-color approach, achieving 1.5 × 10 −13 at τ = 1 s [37]. A further key advantage lies in the flexibility to change the intermediate state detuning which has been explored to suppress light shifts [39,40], as well as a theoretical study suggesting this flexibility can also be used to suppress temperature shifts [41]. Therefore it would be instrumental to explore if this two-color excitation approach can exhibit equivalent stabilities to a direct two photon excitation and further, how we may simplify and enhance this approach to ultimately reach a goal of a compact instrument based on this premise. ...
- Citing Article
November 2022
Physical Review A
... Improvements in link stability may be possible by using optical methods of generating low-phase noise RF signals. 45,46 The noise floor of the system can be reached at shorter averaging times by tuning the repetition rate difference between the two combs to produce higher update rates. With a 100 kHz update rate, the system could reach the noise floor of 15 fs after averaging for 2 ms, as shown in Fig. 4. ...
- Citing Article
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March 2022
... 一种是通过反馈控制光梳重复频率 frep 来稳定光梳的一条特定谱线到光学参考 [55,56] , 而光 梳载波包络频率 fceo 被锁定到微波频率参考, 因此 frep 可以作为种子源, 通过使用如直接数字合成器(DDS) 的下变频产生时钟频率. 另一种是传递振荡器技术 [57,58] , 即基于合理的混频, 滤波和分频以免疫光梳噪 声的影响, 再通过电学网络可将光频率转换为具有 超高同步性的微波频率. Page 8 of 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 其中∆qi(t)表征激光频率和时钟频率间的同源水平, 该噪声在空间引力波探测科学频段内已被实验证明 是非常小的 [60] , 因此本文分析中将忽略这一项的影 响. 基于式 (19), 式(7-8)所示的六个组合数据流可被 重写为: (20) 从上式可见, 在光梳连接的情况下, 时钟噪声可被等 效地转换为激光频率噪声, 因此只需利用光梳 TDI 算法抑制该等效的激光频率噪声即可 [25,26] . ...
Reference:
空间引力波探测中的时钟噪声抑制技术研究进展
- Citing Article
- Full-text available
February 2022
... The beat notes can be considered equivalent to the sinusoidal intensity modulations on continuous-wave lasers used for phase-based distance estimation in high-end electro-optical distance measurement (EDM) or laser scanning instruments. The intermode beating approach has been demonstrated as a robust alternative to this established technique (Minoshima and Matsumoto, 2000, Minoshima et al., 2006, Doloca et al., 2010, Jang et al., 2014, providing multiple high quality and high bandwidth modulation signals suitable for EDM without using any electrical or optical modulators. This yields lower instrumental errors by reducing crosstalk while enabling flexible multi-frequency measurements that deliver high resolution and high non-ambiguity and enhance mixed pixel detectability. ...
- Citing Conference Paper
- Full-text available
August 2021
... To evaluate the relative frequency stability between the two frequency combs of the two lasers in the short term, we detected the beat notes (f beat1 , f beat2 ) between each frequency comb and a narrow-linewidth single-frequency laser (RIO, PLANEX) at 1566 nm with a high signal-tonoise-ratio (SNR) of approximately 30 dB at an RBW of 300 kHz [ Fig. 3(a), (b)]. The phases of the two signals were measured using a multichannel digital phase meter [33], simultaneously. The phase noises of the two f beat signals and the difference ∆f beat yielded a common-mode noise rejection ratio of 50 dB at a frequency of approximately 1 Hz [ Fig. 3(c)]. ...
- Citing Preprint
September 2020
... An increased number of comb teeth facilitates the acquisition of more detailed information in absorption spectroscopy [2]. Moreover, the high-frequency microwave signals generated from these lasers exhibit significantly lower noise than those produced by crystal oscillators [3]. Furthermore, GHz mode-locked lasers find extensive applications in ranging, imaging, and astronomical spectroscopy. ...
- Citing Article
- Full-text available
August 2020