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11 pages, 5675 KiB

Open AccessCommunication

780 nm Narrow Linewidth External Cavity Diode Laser for Quantum Sensing

by Junzhu Ye, Chenggang Guan, Puchu Lv, Weiqi Wang, Xuan Chen, Ziyi Wang, Yifan Xiao, Linfeng Zhan, Jiaoli Gong and Yucheng Yao

Sensors 2024, 24(22), 7237; https://doi.org/10.3390/s24227237 - 13 Nov 2024

Cited by 1 | Viewed by 2157

Abstract

To meet the demands of laser communication, quantum precision measurement, cold atom technology, and other fields for narrow linewidth and low-noise light sources, an external cavity diode laser (ECDL) operating in the wavelength range around 780 nm was set up with a Fabry–Pérot [...] Read more.

To meet the demands of laser communication, quantum precision measurement, cold atom technology, and other fields for narrow linewidth and low-noise light sources, an external cavity diode laser (ECDL) operating in the wavelength range around 780 nm was set up with a Fabry–Pérot etalon (F–P) and an interference filter (IF) in the experiment. The interference filter type ECDL (IF–ECDL) with butterfly-style packaging configuration has continuous wavelength tuning within a specified range through precise temperature and current control and has excellent single-mode characteristics. Experimental results indicate that the output power of the IF–ECDL is 14 mW, with a side-mode suppression ratio (SMSR) of 54 dB, a temperature-controlled mode-hop-free tuning range of 527 GHz (1.068 nm), and an output linewidth of 570 Hz. Compared to traditional lasers operating at 780 nm, the IF–ECDL exhibits narrower linewidth, lower noise, and higher spectral purity, and its dimensions are merely 25 × 15 × 8.5 mm³ weighing only 19.8 g, showcasing remarkable miniaturization and lightweight advantages over similar products in current research fields. Full article

(This article belongs to the Section Optical Sensors)

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15 pages, 10380 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

THz Filters Made by Laser Ablation of Stainless Steel and Kapton Film

by Molong Han, Daniel Smith, Soon Hock Ng, Zoltan Vilagosh, Vijayakumar Anand, Tomas Katkus, Ignas Reklaitis, Haoran Mu, Meguya Ryu, Junko Morikawa, Jitraporn Vongsvivut, Dominique Appadoo and Saulius Juodkazis

Micromachines 2022, 13(8), 1170; https://doi.org/10.3390/mi13081170 - 25 Jul 2022

Cited by 4 | Viewed by 2753

Abstract

THz band-pass filters were fabricated by femtosecond-laser ablation of 25-

μ

m-thick micro-foils of stainless steel and Kapton film, which were subsequently metal coated with a ∼70 nm film, closely matching the skin depth at the used THz spectral window. Their spectral performance [...] Read more.

THz band-pass filters were fabricated by femtosecond-laser ablation of 25-

μ

m-thick micro-foils of stainless steel and Kapton film, which were subsequently metal coated with a ∼70 nm film, closely matching the skin depth at the used THz spectral window. Their spectral performance was tested in transmission and reflection modes at the Australian Synchrotron’s THz beamline. A 25-

μ

m-thick Kapton film performed as a Fabry–Pérot etalon with a free spectral range (

F S R

) of 119 cm

^{- 1}

, high finesse

F_{c} \approx 17

, and was tuneable over ∼

10 μ

m (at ∼5 THz band) with

β = 30^{\circ}

tilt. The structure of the THz beam focal region as extracted by the first mirror (slit) showed a complex dependence of polarisation, wavelength and position across the beam. This is important for polarisation-sensitive measurements (in both transmission and reflection) and requires normalisation at each orientation of linear polarisation. Full article

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11 pages, 1963 KiB

Open AccessArticle

Frequency Conversion Interface towards Quantum Network: From Atomic Transition Line to Fiber Optical Communication Band

by Shujing Li, Jiaxin Bao, Qiqi Deng, Lirong Chen and Hai Wang

Appl. Sci. 2022, 12(13), 6522; https://doi.org/10.3390/app12136522 - 27 Jun 2022

Cited by 2 | Viewed by 2273

Abstract

Quantum repeater is a key component of quantum network, and atomic memory is one of the important candidates for constructing quantum repeater. However, the atomic transition wavelength is not suitable for long-distance transmission in optical fiber. To bridge atomic memory and fiber communication, [...] Read more.

Quantum repeater is a key component of quantum network, and atomic memory is one of the important candidates for constructing quantum repeater. However, the atomic transition wavelength is not suitable for long-distance transmission in optical fiber. To bridge atomic memory and fiber communication, we demonstrate a frequency conversion interface from rubidium D1 line (795 nm) to the optical communication L-band (1621 nm) based on difference frequency generation. To reduce broadband noise of spontaneous Raman scattering caused by strong pumping light, we use a combination of two cascaded etalons and a Fabry-Perot cavity with low finesse to narrow the noise bandwidth to 11.7 MHz. The filtering system is built by common optical elements and is easy to use; it can be widely applied in frequency conversion process. We show that the signal-noise ratio of the converted field is good enough to reduce the input photon number below 1 under the condition of low external device conversion efficiency (0.51%) and large duration of input pulse (250 ns). The demonstrated frequency conversion interface has important potential application in quantum networks. Full article

(This article belongs to the Special Issue New Chances of Optical Fiber Network)

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8 pages, 1951 KiB

Open AccessCommunication

A Narrow-Linewidth Optical Parametric Oscillator Inserted with Fabry–Perot Etalon

by Xuefang Hu, Changgui Lu, Niuniu Wang, Zhengqing Qi and Yiping Cui

Photonics 2021, 8(12), 528; https://doi.org/10.3390/photonics8120528 - 24 Nov 2021

Viewed by 2443

Abstract

Nowadays, the Fabry–Perot etalon (F–P) has been widely utilized in the optical parametric oscillator (OPO) to improve the filtering performance. In this paper, we reported an F–P etalon composed of two ultra-thin silicon wafers spaced with the air. The linewidth of the signal [...] Read more.

Nowadays, the Fabry–Perot etalon (F–P) has been widely utilized in the optical parametric oscillator (OPO) to improve the filtering performance. In this paper, we reported an F–P etalon composed of two ultra-thin silicon wafers spaced with the air. The linewidth of the signal laser and the threshold are 0.03 nm and 0.6 W, respectively when the proposed etalon is employed to a OPO system based on the MgO-doped LiNbO₃ (MgO: PPLN). A stabilized output at 1492.4 nm is obtained, and a tunable, high-precision filtering performance can be achieved by varying the gap distance of the F–P etalon arbitrarily due to its ultra-thin thickness. In addition, the F–P etalon can work on a very wide bandwidth due to its weak absorption during the infrared and terahertz waveband. The high-precision tuning capability and wide-band function of proposed etalon may benefit many applications, including spectroscopy, filtering, and optical communication. Full article

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8 pages, 2761 KiB

Open AccessArticle

Polymer-Stabilized Blue Phase and Its Application to a 1.5 µm Band Wavelength Selective Filter

by Seiji Fukushima, Kakeru Tokunaga, Takuya Morishita, Hiroki Higuchi, Yasushi Okumura, Hirotsugu Kikuchi and Hidehisa Tazawa

Crystals 2021, 11(9), 1017; https://doi.org/10.3390/cryst11091017 - 25 Aug 2021

Cited by 3 | Viewed by 2326

Abstract

The use of polymer-stabilized blue phase (PSBP) including a tolane-type liquid crystal was investigated to develop a voltage-controlled wavelength selective filter for wavelength-division-multiplexing optical fiber network. It was found that the tolane-type liquid crystal introduction can increase both a blue-phase temperature range and [...] Read more.

The use of polymer-stabilized blue phase (PSBP) including a tolane-type liquid crystal was investigated to develop a voltage-controlled wavelength selective filter for wavelength-division-multiplexing optical fiber network. It was found that the tolane-type liquid crystal introduction can increase both a blue-phase temperature range and a Kerr coefficient. A Fabry–Perot etalon filled with PSBP functioned as a wavelength selective filter, as expected. The tuning wavelength range was 62 nm although peak transmission was not as high as expected. Numerical analysis suggested that light absorption in transparent electrodes may cause the issue. Minor change to the etalon structure will result in improved performance. Full article

(This article belongs to the Special Issue Liquid Crystal Optics for Applications)

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15 pages, 3597 KiB

Open AccessArticle

Temperature Control for an Intra-Mirror Etalon in Interferometric Gravitational Wave Detector Fabry–Perot Cavities

by Jonathan Brooks, Maddalena Mantovani, Annalisa Allocca, Julia Casanueva Diaz, Vincenzo Dattilo, Alain Masserot and Paolo Ruggi

Galaxies 2020, 8(4), 80; https://doi.org/10.3390/galaxies8040080 - 1 Dec 2020

Cited by 5 | Viewed by 3027

Abstract

The sensitivity of interferometric gravitational wave detectors is optimized, in part, by balanced finesse in the long Fabry–Perot arm cavities. The input test mass mirrors of Advanced Virgo feature parallel faces, which creates an etalon within the substrate, adding variability in the total [...] Read more.

The sensitivity of interferometric gravitational wave detectors is optimized, in part, by balanced finesse in the long Fabry–Perot arm cavities. The input test mass mirrors of Advanced Virgo feature parallel faces, which creates an etalon within the substrate, adding variability in the total mirror reflectivity, in order to correct imbalanced finesse due to manufacturing tolerances. Temperature variations in mirror substrate change the optical path length primarily through varying the index of refraction and are tuned to correct for a finesse imbalance of up to 2.8% by a full etalon fringe of 0.257 K. A negative feedback control system was designed to control the mirror temperature by using an electrical resistive heating belt actuator for a heat transfer process modeled as a two-pole plant. A zero controller filter was designed which achieves temperature control within 2.3% of the etalon fringe and recovers to within 10% of the working point within 32 hours after a step input of one etalon fringe. A preliminary unlock condition control designed to compensate when the interferometer unlocks shows that the control remains stable even after a drastic change in the plant due to the absence of the laser heating. Further improvements to the control must also consider the full heat transfer mechanisms by using modern control state space models. Full article

(This article belongs to the Special Issue Gravitational Wave Detectors)

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12 pages, 5051 KiB

Open AccessArticle

Tunable Fabry-Perot Interferometer Designed for Far-Infrared Wavelength by Utilizing Electromagnetic Force

by Dong Geon Jung, Jun Yeop Lee, Jae Keon Kim, Daewoong Jung and Seong Ho Kong

Sensors 2018, 18(8), 2572; https://doi.org/10.3390/s18082572 - 6 Aug 2018

Cited by 5 | Viewed by 5559

Abstract

A tunable Fabry-Perot interferometer (TFPI)-type wavelength filter designed for the long-wavelength infrared (LWIR) region is fabricated using micro electro mechanical systems (MEMS) technology and the novel polydimethylsiloxane (PDMS) micro patterning technique. The structure of the proposed infrared sensor consists of a Fabry-Perot interferometer [...] Read more.

A tunable Fabry-Perot interferometer (TFPI)-type wavelength filter designed for the long-wavelength infrared (LWIR) region is fabricated using micro electro mechanical systems (MEMS) technology and the novel polydimethylsiloxane (PDMS) micro patterning technique. The structure of the proposed infrared sensor consists of a Fabry-Perot interferometer (FPI)-based optical filter and infrared (IR) detector. An amorphous Si-based thermal IR detector is located under the FPI-based optical filter to detect the IR-rays filtered by the FPI. The filtered IR wavelength is selected according to the air etalon gap between reflectors, which is defined by the thickness of the patterned PDMS. The 8 μm-thick PDMS pattern is fabricated on a 3 nm-thick Al layer used as a reflector. The air etalon gap is changed using the electromagnetic force between the permanent magnet and solenoid. The measured PDMS gap height is about 2 μm, ranging from 8 μm to 6 μm, with driving current varying from 0 mA to 600 mA, resulting in a tunable wavelength range of 4 μm. The 3-dB bandwidth (full width at half maximum, FWHM) of the proposed filter is 1.5 nm, while the Free Spectral Range (FSR) is 8 μm. Experimental results show that the proposed TFPI can detect a specific wavelength at the long LWIR region. Full article

(This article belongs to the Special Issue Infrared Sensors and Technologies)

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10 pages, 1961 KiB

Open AccessArticle

Acousto-Optic–Based Wavelength-Comb-Swept Laser for Extended Displacement Measurements

by Nam Su Park, Soo Kyung Chun, Ga-Hee Han and Chang-Seok Kim

Sensors 2017, 17(4), 740; https://doi.org/10.3390/s17040740 - 31 Mar 2017

Cited by 12 | Viewed by 6005

Abstract

We demonstrate a novel wavelength-comb-swept laser based on two intra-cavity filters: an acousto-optic tunable filter (AOTF) and a Fabry-Pérot etalon filter. The AOTF is used for the tunable selection of the output wavelength with time and the etalon filter for the narrowing of [...] Read more.

We demonstrate a novel wavelength-comb-swept laser based on two intra-cavity filters: an acousto-optic tunable filter (AOTF) and a Fabry-Pérot etalon filter. The AOTF is used for the tunable selection of the output wavelength with time and the etalon filter for the narrowing of the spectral linewidth to extend the coherence length. Compared to the conventional wavelength-swept laser, the acousto-optic–based wavelength-comb-swept laser (WCSL) can extend the measureable range of displacement measurements by decreasing the sensitivity roll-off of the point spread function. Because the AOTF contains no mechanical moving parts to select the output wavelength acousto-optically, the WCSL source has a high wavenumber (k) linearity of R² = 0.9999 to ensure equally spaced wavelength combs in the wavenumber domain. Full article

(This article belongs to the Special Issue Laser Sensors for Displacement, Distance, Flow, Velocity and Vibrations Measurements)

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15 pages, 3830 KiB

Open AccessArticle

An Optoelectronic Equivalent Narrowband Filter for High Resolution Optical Spectrum Analysis

by Kunpeng Feng, Jiwen Cui, Hong Dang, Weidong Wu, Xun Sun, Xuelin Jiang and Jiubin Tan

Sensors 2017, 17(2), 348; https://doi.org/10.3390/s17020348 - 10 Feb 2017

Cited by 9 | Viewed by 5119

Abstract

To achieve a narrow bandwidth optical filter with a wide swept range for new generation optical spectrum analysis (OSA) of high performance optical sensors, an optoelectronic equivalent narrowband filter (OENF) was investigated and a swept optical filter with bandwidth of several MHz and [...] Read more.

To achieve a narrow bandwidth optical filter with a wide swept range for new generation optical spectrum analysis (OSA) of high performance optical sensors, an optoelectronic equivalent narrowband filter (OENF) was investigated and a swept optical filter with bandwidth of several MHz and sweep range of several tens of nanometers was built using electric filters and a sweep laser as local oscillator (LO). The principle of OENF is introduced and analysis of the OENF system is presented. Two electric filters are optimized to be RBW filters for high and medium spectral resolution applications. Both simulations and experiments are conducted to verify the OENF principle and the results show that the power uncertainty is less than 1.2% and the spectral resolution can reach 6 MHz. Then, a real-time wavelength calibration system consisting of a HCN gas cell and Fabry–Pérot etalon is proposed to guarantee a wavelength accuracy of ±0.4 pm in the C-band and to reduce the influence of phase noise and nonlinear velocity of the LO sweep. Finally, OSA experiments on actual spectra of various optical sensors are conducted using the OENF system. These experimental results indicate that OENF system has an excellent capacity for the analysis of fine spectrum structures. Full article

(This article belongs to the Section Physical Sensors)

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