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Continuous-wave 6-dB-squeezed light with 2.5-THz-bandwidth from single-mode PPLN waveguide
摘要： Terahertz (THz)-bandwidth continuous-wave (CW) squeezed light is essential for integrating quantum processors with time-domain multiplexing (TDM) by using optical delay line interferometers. Here, we utilize a single-pass optical parametric amplifier (OPA) based on a single-spatial-mode periodically poled ZnO:LiNbO3 waveguide, which is directly bonded onto a LiTaO3 substrate. The single-pass OPA allows THz bandwidth, and the absence of higher-order spatial modes in the single-spatial-mode structure helps avoid degradation of squeezing. In addition, the directly bonded ZnO-doped waveguide has durability for high-power pump and shows small photorefractive damage. Using this waveguide, we observe CW 6.3-dB squeezing at 20-MHz sideband by balanced homodyne detection. This is the first realization of CW squeezing with a single-pass OPA at a level exceeding 4.5 dB, which is required for the generation of a two-dimensional cluster state. Furthermore, the squeezed light shows 2.5-THz spectral bandwidth. The squeezed light will lead to the development of a high-speed on-chip quantum processor using TDM with a centimeter-order optical delay line.
关键词： terahertz-bandwidth,quantum information processing,squeezed light,continuous-wave,single-mode PPLN waveguide
更新于2025-09-19 17:13:59
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4-dB Quadrature Squeezing With Fiber-Coupled PPLN Ridge Waveguide Module
摘要： We have developed an optical parametric amplification module for quadrature squeezing with input and output ports coupled with optical fibers for both fundamental and second harmonic. The module consists of a periodically poled LiNbO3 ridge waveguide fabricated with dry etching, dichroic beamsplitters, lenses and four optical fiber pigtales. The high durability of the waveguide and the good separation of squeezed light from a pump beam by the dichroic beamsplitter enable us to inject intense continuous-wave pump light with the power of over 300 mW. We perform ?4.0±0.1 dB of noise reduction for a vacuum state at 1553.3 nm by using a fiber-optics-based measurement setup, which consists of a fiber-optic beamsplitter and a homemade fiber-receptacle balanced detector. The intrinsic loss of the squeezed vacuum in the module is estimated to be 25%. Excluding the extrinsic loss of the measuremental system, the squeezing level in the output fiber of the module is estimated to be ?5.7±0.1 dB. A modularized alignment-free fiber-coupled quadrature squeezer could help to realize quantum information processing with fiber optics.
关键词： PPLN waveguide,fiber optics,squeezed light
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Frequency-Multiplexed Singly-Resonant Photon Pairs from a Quadratic Nonlinear Waveguide Resonator
摘要： Frequency multiplexed photon pair generation has been actively studied for efficient and large-scale photonic quantum information processing [1-3]. In these demonstrations, photon pair generators were realized by using an optical parametric oscillator (OPO) far below threshold; a nonlinear optical medium was inside or integrated with an optical cavity, and a sufficiently weak pump light for the photon pair generation was used. However, to the best of our knowledge, all of the previous demonstrations for frequency multiplexed photon pair generation have used a doubly-resonant OPO which confines both the signal and the idler photons, or a triply-resonant OPO which additionally confines the pump light. In this study, we demonstrate a frequency multiplexed photon pair generation based on a singly-resonant (SR) OPO configuration which confines only one half of the photon pair. We used a periodically-poled lithium niobate (PPLN) waveguide as a monolithically-integrated quadratic nonlinear waveguide resonator; dielectric multilayers are directly formed at the end faces of the PPLN waveguide such that only the signal photon around 1600 nm of the photon pair is confined in the resonator and the idler photon around 1522 nm and the pump light at 780 nm are not confined. In the SR photon pair, in spite of no cavity configuration for the idler photons, not only the signal photons but also the idler photons have comb-like spectra as if both of them are confined in the cavity. In addition, there is not missing teeth region observed in multiple resonant OPO configuration known as the cluster effect [4,5]. As a result, a wide-band frequency multiplexed photon pair generation can be possible. The photon pair generator will be useful for an efficient photonic quantum information processing and a frequency-domain photon manipulation with the use of frequency-domain optical elements [6-9].
关键词： singly-resonant OPO,PPLN waveguide,photon pair generation,quantum information processing,frequency multiplexed
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - An Iodine-Stabilized Laser using a 1542-nm Light Source
摘要： Frequency-stabilized lasers at the telecom wavelengths are of great interest for a wide range of applications, including wavelength standards for optical communication systems [1], and an absolute frequency marker of an optical frequency comb. Especially in astro-comb application [2], it is considered to be a good candidate of an optical frequency reference laser since it has a good frequency connection to a fiber-based frequency comb. Frequency-stabilized lasers at the telecom wavelengths are usually based on the acetylene combination band transitions [1], however, these transitions are relatively weak for frequency stabilization to realize high stability. On the other hand, molecular iodine has very strong absorption lines in the 500-nm wavelength region. Highly stable and reliable iodine-stabilized lasers have been realized by using frequency-doubled 1-μm lasers [3]. In this study, we developed an iodine-stabilized laser at the telecom wavelength by using frequency-tripled 1542-nm laser. In the previous study [4], third harmonic generation (THG) of a 1.5 μm laser has been demonstrated by using two periodically poled lithium niobate (PPLN) waveguides. On the other hand, as shown in the inset of Fig. 1(a), we used a dual-pitch PPLN waveguide (NTT Electronics Corporation WS-0514-000-A-C-C-TEC) which consists of two stages of PPLN with different polling periods for second harmonic generation (SHG, 1542 nm →771 nm) and sum frequency generation (SFG, 1542 nm + 771 nm →514 nm). Figure 1(a) shows the phase-matching curve of the waveguide for both SHG and SFG. The phase-matching curve for SHG is broadened because the PPLN has a chirped polling period in the first stage, which enables the satisfaction of both phase-matching conditions for SHG and SFG simultaneously. A maximum power of 1.7 mW was obtained when the 1.5-μm-laser output power was 200 mW. Doppler-free transition signals of molecular iodine were observed by saturation spectroscopy based on the modulation transfer technique [3]. The inset of Fig. 1(b) shows the obtained entire hyperfine components of the R(73)46-0 transition at 514 nm. The laser frequency was stabilized to the a1 hyperfine component of the observed transition. To evaluate the stability of the laser frequency, we measured the laser frequency using an optical frequency comb referenced to a H-maser. Figure 1(b) shows the measured Allan standard deviation that indicates the frequency stability of the developed laser. The Allan standard deviation was 1×10-11 for a 1-s averaging time. The short-term stability, limited by the signal-to-noise ratio of the transition signal, will be improved by increasing the laser power using a high-power erbium-doped fiber amplifier. As for the long-term stability, we need to verify the uncertainty factors that cause the long-term drift and remove them as possible.
关键词： iodine-stabilized laser,frequency-tripled 1542-nm laser,dual-pitch PPLN waveguide,Frequency-stabilized lasers,telecom wavelengths
更新于2025-09-16 10:30:52
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Frequency-Multiplexed Photon Pairs Over 1000 Modes from a Quadratic Nonlinear Optical Waveguide Resonator with a Singly Resonant Configuration
摘要： We demonstrate a frequency multiplexed photon pair generation based on a quadratic nonlinear optical waveguide inside a cavity which confines only signal photons without confining idler photons and the pump light. We monolithically constructed the photon pair generator by a periodically poled lithium niobate (PPLN) waveguide with a high reflective coating for the signal photons around 1600 nm and with antireflective coatings for the idler photons around 1520 nm and the pump light at 780 nm at the end faces of the PPLN waveguide. We observed a comblike photon pair generation with a mode spacing of the free spectral range of the cavity. Unlike the conventional multiple resonant photon pair generation experiments, the photon pair generation was incessant within a range of 80 nm without missing teeth due to a mismatch of the energy conservation and the cavity resonance condition of the photons, resulting in over 1000-mode frequency multiplexed photon pairs in this range.
关键词： frequency multiplexed photon pair generation,photon pair generator,PPLN waveguide,quadratic nonlinear optical waveguide,singly resonant configuration
更新于2025-09-12 10:27:22