skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Synthetic FM triplet for AM-free precision laser stabilization and spectroscopy
The Pound–Drever–Hall (PDH) cavity-locking scheme has found prevalent uses in precision optical interferometry and laser frequency stabilization. A form of frequency modulation spectroscopy, PDH enjoys superior signal-to-noise recovery, large acquisition dynamic range, wide servo bandwidth, and robust rejection of spurious effects. However, residual amplitude modulation at the signal frequency, while significantly suppressed, still presents an important concern for further advancing the state-of-the-art performances. Here we present a simplified and improved scheme for PDH using an acousto-optic modulator to generate digital phase reference sidebands instead of the traditionally used electro-optic modulator approach. We demonstrate four key advantages: (1) the carrier and two modulation tones are individually synthesized and easily reconfigured, (2) robust and orthogonal control of the modulated optical field is applied directly to the amplitude and phase quadratures, (3) modulation synthesis, demodulation, and feedback are implemented in a self-contained and easily reproducible electronic unit, and (4) superior active and passive control of residual amplitude modulation is achieved, especially when the carrier power is vanishingly low. These distinct merits stimulate new ideas on how we optimally enact PDH for a wide range of applications.  more » « less
Award ID(s):
1734006 2016244
PAR ID:
10485063
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
Optical Society of America
Date Published:
Journal Name:
Optica
Volume:
11
Issue:
1
ISSN:
2334-2536
Format(s):
Medium: X Size: Article No. 58
Size(s):
Article No. 58
Sponsoring Org:
National Science Foundation
More Like this
  1. (, 2020 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting)
    null (Ed.)
    On chip antennas with integrated electro-optic modulators (EOMs) are attractive for millimeter wave applications. Such EOMs are placed at the antenna feed and enable the mixing of the incoming millimeter wave (mm-wave) signal with an optical carrier. As such, the mm-wave capture is turned into an optical signal that can be easily processed for imaging using standard infrared cameras. Our proposed on-chip antenna with the EOM modulator operated at 94 GHz or 77 GHz, with the antenna tuned at that frequency. For high modulation efficiency, it is critical that the modulator region is as small as possible with the optical waveguide leading to the EOM, also being well-matched. Notably, the enhanced field at the antenna feed leads to higher modulation efficiency and sensitivity. Therefore, an optimum antenna design must hasve as large as possible field strength at the feed. 
    more » « less
  2. ; ; ; (, Optics Express)
    We propose an on-chip triply resonant electro-optic modulator architecture for RF-to-optical signal conversion and provide a detailed theoretical analysis of the optimal “circuit-level” device geometries and their performance limits. The designs maximize the RF-optical conversion efficiency through simultaneous resonant enhancement of the RF drive signal, a continuous-wave (CW) optical pump, and the generated optical sideband. The optical pump and sideband are resonantly enhanced in respective supermodes of a two-coupled-cavity optical resonator system, while the RF signal can be enhanced in addition by an LC circuit formed by capacitances of the optical resonator active regions and (integrated) matching inductors. We show that such designs can offer 15-50 dB improvement in conversion efficiency over conventional microring modulators. In the proposed configurations, the photon lifetime (resonance linewidth) limits the instantaneous RF bandwidth of the electro-optic response but does not limit its central RF frequency. The latter is set by the coupling strength between the two coupled cavities and is not subject to the photon lifetime constraint inherent to conventional singly resonant microring modulators. This feature enables efficient operation at high RF carrier frequencies without a reduction in efficiency commonly associated with the photon lifetime limit and accounts for 10-30 dB of the total improvement. Two optical configurations of the modulator are proposed: a “basic” configuration with equal Q-factors in both supermodes, most suitable for narrowband RF signals, and a “generalized” configuration with independently tailored supermode Q-factors that supports a wider instantaneous bandwidth. A second significant 5-20 dB gain in modulation efficiency is expected from RF drive signal enhancement by integrated LC resonant matching, leading to the total expected improvement of 15-50 dB. Previously studied triply-resonant modulators, with coupled longitudinal (across the free spectral range (FSR)) modes, have large resonant mode volume for typical RF frequencies, which limits the interaction between the optical and RF fields. In contrast, the proposed modulators support maximally tightly confined resonant modes, with strong coupling between the mode fields, which increases and maintains high device efficiency across a range of RF frequencies. The proposed modulator architecture is compact, efficient, capable of modulation at high RF carrier frequencies and can be applied to any cavity design or modulation mechanism. It is also well suited to moderate Q, including silicon, implementations, and may be enabling for future CMOS RF-electronic-photonic systems on chip. 
    more » « less
  3. ; ; (, Optics Express)
    We demonstrate a widely spaced, stabilized, and self-referenced opto-electronic oscillator driven electro-optic modulator based optical frequency comb. Using an ultra-stable Fabry-Perot etalon as a stable reference, we simultaneously stabilize a CW laser and generate a low noise and stable RF oscillation used to drive an electro-optic comb. In such a manner, the Fabry-Perot etalon pins both the carrier-envelope-offset frequency (fceo) and the repetition rate of the comb in place (frep), eliminating the need for an external RF oscillator. Usage of the ultra-stable Fabry-Perot etalon as both an optical and RF reference allows the removal of an external RF oscillator. Additionally, we determined the key parameters in producing high contrast ultrashort pulses necessary for coherent octave spanning supercontinuum generation using long and weak pulses associated with electro-optic modulator based combs. By using a monolithically fiber based pulse compression scheme, we produced ultrashort pulses to facilitate measuring the carrier-envelope-offset frequency, allowing for the first self-starting, self-stabilized, and self-referenced opto-electronic oscillator driven electro-optic modulator based optical frequency comb. 
    more » « less
  4. ; ; ; (, Review of Scientific Instruments)
    The small signal-to-noise ratio (SNR) of conventional laser induced fluorescence (LIF) measurements using a continuous wave laser, either diode or dye, is typically overcome by amplitude modulating the laser at a specific frequency and then using lock-in amplification to extract the signal from measurement noise. Here, we present LIF measurements of the neutral helium velocity distribution function in an rf plasma using frequency modulated (FM) laser injection. A pulse train of 100% amplitude modulation is generated synthetically with a random sequence of pulse lengths. The FM signal then drives an acoustic optic modulator placed in the path of the injection beam in an LIF measurement. The signal from a fast photomultiplier tube is digitized and cross-correlated with the known modulation signal. The resultant FM-based LIF signal outperforms a conventional lock-in-based LIF measurement on the same plasma in terms of SNR and precision. 
    more » « less
  5. ; ; (, Applied Optics)
    Active mode mismatch sensing and control can facilitate optimal coupling in optical cavity experiments such as interferometric gravitational wave detectors. In this paper, we demonstrate a radio-frequency (RF) beam wavefront curvature modulation-based mode mismatch sensing scheme inspired by the previously proposed RF beam jitter alignment sensing scheme. The proposed mode mismatch sensing scheme uses an electro-optic lens (EOL) device that is designed to provide the required beam wavefront curvature actuation, as well as a mode converting telescope that rephases the RF second-order modes and generates a non-vanishing mode mismatch sensing signal. We carefully investigate the total second-order mode generation from the wavefront actuation both analytically and numerically, taking the effects of Gaussian beam size evolution and the second-order mode phase mismatch cancellation into consideration. We demonstrate the second-order mode generation as a function of the incident beam waist size and the electro-optic crystal size which, along with a “trade-off” consideration of the beam size at the edges of the crystal and the clipping loss, provides us with guidance for designing the beam profile that interacts with the crystal to improve the EOL modulation efficiency. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email