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Development of an optical pressure measurement system using an external cavity diode laser with a wide tunable frequency range
摘要： Optical pressure measurement systems can precisely measure pressure from vacuum to high pressure with a single apparatus. However, the continuously measurable range without interrupting measurement is limited to less than 1 kPa. In this study, an optical pressure measurement system with a wide continuous measurable range was developed. The optical system can continuously measure a pressure range of 18 kPa when using nitrogen gas by using a Littrow external cavity diode laser as its light source. First, discrete pressure points from vacuum to atmospheric pressure were measured. The repeatability and non-linearity of the differences between the measured values had standard deviations of 0.1 Pa and 0.5 Pa, respectively. Next, a pressure range from 91 kPa to 109 kPa was continuously measured. The results showed that the linearity characteristics of gauges as a function of pressure can be evaluated precisely using our optical pressure measurement system.
关键词： optical pressure measurement,external cavity diode laser,refractive index,wide tunable frequency range,Fabry-Perot cavity
更新于2025-09-12 10:27:22
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A Fast and Reproducible ELISA Laser Platform for Ultrasensitive Protein Quantification
摘要： Optofluidic lasers are currently of high interest for sensitive, intra-cavity, biochemical analysis. In comparison with conventional methods such as fluorescence and colorimetric detection, optofluidic lasers provide a method for amplifying small concentration differences in the gain medium, thus achieving high sensitivity. Here we report the development of an on-chip ELISA (enzyme-linked immunosorbent assay) laser platform that is able to complete an assay in short amount of time with small sample/reagent volumes, large dynamic range, and high sensitivity. The arrayed micro-scale reaction wells in the ELISA lasers can be microfabricated directly on dielectric mirrors, thus significantly improving the quality of the reaction wells and detection reproducibility. The details of the fabrication and characterization of those reaction wells on the mirror are described and the ELISA laser assay protocols are developed. Finally, we applied the ELISA laser to detecting IL-6, showing that a detection limit of about 0.1 pg/mL can be achieved in 1.5 hours with 15 μL of sample/reagents per well. This work pushes the ELISA laser a step closer to solving problems in real-world biochemical analysis.
关键词： Interleukin-6,Fabry-Perot cavity,Immunoassay,Optofluidic laser,Microfabrication,ELISA
更新于2025-09-12 10:27:22
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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) - Coherent Coupling of Single Molecules to Microresonators
摘要： Many interesting proposals in quantum optics and light-matter interaction rely on having multiple quantum emitters well-coupled to a single mode of light. Of particular interest are cases where several identical emitters couple to a one-dimensional (1D) photonic medium. Recently, we presented such a system by evanescent coupling of organic dye molecules to the same guided mode of an on-chip subwavelength waveguide [1]. While this coupling allowed us to demonstrate up to 7.5% transmission extinction of the propagating light by a single molecule, it is still not sufficient for achieving higher-order effects such as photon-mediated interaction of multiple emitters coupled to the same waveguide. One way to improve the waveguide-emitter coupling is the use of resonant structures, as was recently shown in our laboratory for a microscopic open Fabry-Perot cavity [2]. In that work, we demonstrated a strong Purcell broadening of the molecular emission, and almost complete extinction of the resonant cavity transmission. In the current work, we extended this approach to on-chip racetrack resonators [3], as shown in Fig. 1(a). In such a geometry, the coupling enhancement is proportional to the number of photon round trips inside the resonator, which is roughly equal to F/π, where F is the resonator finesse. Currently, our resonators can reach finesse as high as 18 when exposed to the surrounding organic matrix at cryogenic temperatures, leading to enhanced extinction dips up to 22%, as shown in the orange plot in Fig. 1(b). We additionally verify the molecule-resonator coupling by localizing the position of the molecule (marked by a white arrow in Fig. 1(a)), and by observing the expected peak in the transmission port of the resonator (blue line in Fig. 1(b)). Finally, we perform a comparison to a single waveguide on the same chip, which still showed maximal extinction of only 7%, consistent with the previous results. We discuss the observed degree of enhancement, compare it with the predictions of theoretical calculations, and evaluate future strategies for reaching on-chip near-unity coupling efficiency as well as many-emitter effects, such as light localization and generation of polaritonic states [4].
关键词： racetrack resonators,light-matter interaction,waveguide-emitter coupling,photonic medium,quantum optics,Purcell broadening,polaritonic states,resonant structures,Fabry-Perot cavity,quantum emitters
更新于2025-09-12 10:27:22
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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) - Fast Photon Storage in a Fiber-Based Atom-Cavity System
摘要： Miniaturized ?ber-based optical resonators are emerging as a robust and scalable technology for realizing ?ber-based quantum networks. First demonstrated in [1], these cavities have been integrated with a variety of emitters, e.g. atoms, ions and solid-state systems, to build single-photon quantum interfaces. Our system consists of a single 87Rb atom coupled to a high bandwidth (κ = 2π×40 MHz (cid:2) γ), single-sided ?ber Fabry-Perot cavity (FFPC), Fig. 1(a). The unique system of four in-vacuum lenses, with their focal points coinciding with the ?ber-cavity center, provides the necessary optical access for 3D-cooling and trapping, addressing and high resolution ?uorescence imaging of the atoms, Fig. 1(b). For the D2-transition of 87Rb, the strongly coupled atom-cavity system shows a sixfold Purcell broadening and 90% emission into the cavity mode [2]. Here we present deterministic generation and storage of fast photon pulses. For single-photon generation the atomic state is prepared in F = 1 ground state. A π?polarized classical control laser pulse creates a single photon in the cavity mode with an ef?ciency of ～80%, Fig. 1(c). The pulse shape of the emitted single photon can be tailored by the temporal shape of the control pulse on a time scale lower than the atomic excited state lifetime of ～26 ns, Fig. 1(d). For the storage of fast (short) coherent light pulses, the atomic system is prepared in the |F = 2, m f = ?2(cid:4) state by optical pumping. The temporally shaped input coherent laser pulse at the single-photon level incidents on the cavity mirror while a π?polarized control classical laser pulse with an optimized temporal pro?le, dresses the atom-cavity system such that the storage ef?ciency of the input pulse is maximised. We store photon pulses with a temporal width down to 10 ns with an overall ef?ciency of ～5%.
关键词： 87Rb atom,single-photon quantum interfaces,photon storage,fiber Fabry-Perot cavity,fiber-based optical resonators,quantum networks
更新于2025-09-11 14:15:04
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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) - The Photonic Guitar Pickup: A High-Sensitivity, High-Bandwidth Fiber Strain Sensor
摘要： The photonic guitar pickup: a high-sensitivity, high-bandwidth fiber strain sensor. Fiber-strain sensors have found numerous applications from structural health monitoring for vibrations, to pressure and temperature sensing. Many of these sensors exploit the strain-sensitivity of the reflection wavelength of fiber-bragg gratings, (cid:83)-shifted gratings or other waveguide devices. The strain is typically inferred from a change of reflected or transmitted light intensity. Light intensity measurements are not very robust and have an inherently limited accuracy. We propose that a frequency-based strain measurements using fiber Fabry-Perot (FFP) cavities provide not only superior sensitivity but also retain a very high measurement bandwidth. Here, we present a fiber optic vibration sensor based on an FFP cavity, which consists of a matched pair of 23 dB fiber Bragg gratings coupled to a custom-built signal processing circuit. The wavelength of a laser diode is locked to one of the many cavity resonances using the Pound–Drever–Hall scheme. We demonstrate that such a strain sensor has an ultrawide dynamic sensing range, from less than 1 Hz to clinical ultrasound frequencies near 6 MHz. Its linear sensitivity range extends from below 1 n(cid:72) to 2 (cid:80)(cid:72), and its dynamic response limit is as high as 12 m(cid:72)/s. To demonstrate the high fidelity of the strain measurements we attached the FFP cavity sensor to the top plate of an acoustic guitar and recorded several melodies. As expected the sensor system was largely immune to noise arising from optical intensity fluctuations. We made distortion-free audio recordings of musical pieces from infrasound (~8 Hz) to 30 kHz with a 50 dB dynamic range in acoustic power. The remaining noise in our measurements arises from electronic sources and not optical sources, giving hope that future developments may be able to further increase the dynamic range of the measurements, if needed. In separate experiments the same sensor was affixed to the rim of a wineglass and to the side of a steel cantilever to monitor the (photo-)acoustic response of these mechanical resonators to periodic photo-excitation. We found, for example, that the limit of detection for orthophosphate through the photoacoustic excitation of the respective molybdenum-blue complex was below 2 ppm. Finally, the sensor was embedded in tissue phantoms to validate that it accurately responds to low frequencies (heart beat) and high frequencies (ultrasound pulse). In its most recent version the laser driver and the PDH circuit are addressed through a Raspberry-Pi microcontroller, making the sensor system very compact and relatively inexpensive. We propose that sensor systems based on PDH-interrogated FFP-sensor heads are robust and versatile for a large variety of monitoring applications.
关键词： Fabry-Perot cavity,vibration sensor,dynamic range,Pound–Drever–Hall scheme,fiber strain sensor
更新于2025-09-11 14:15:04
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Helium-Based Refractometry for Pressure Measurements in the Range 1–100 kPa
摘要： This paper describes an alternative of pressure measurements based on a helium absolute refractometer at 532 nm. The Fabry-Perot cavity has been characterized from relevant parameters and the resolution in pressure of this new optical pressure sensor is lower than 0.2 Pa.
关键词： Pressure-induced distortion coefficient,Coefficient of thermal expansion,Refractometry,Fabry-Perot cavity,Pressure sensor
更新于2025-09-10 09:29:36
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Normal mode splitting in quantum degenerate Fermi gas in nano-cavity
摘要： We report the normal mode splitting in the fermionic displacement spectrum as a single mode light field interacts with a mechanical mode of ultra-cold quantum degenerate Fermi gas trapped inside a Fabry–Pérot cavity in the strong coupling regime. We explain the normal mode splitting in the outgoing field of the cavity field and in the field quadratures as well. As a function of system parameters, such as coupling strength between fermionic mode and field mode, number of fermionic atoms, cavity decay rate and fluctuations associated with the fermionic mode we explain the phenomenon of normal mode splitting. The low-lying fermions ensemble displays a collective density oscillation associated with particle-hole excitations, which interacts with cavity light field and lead to the observation of NMS in the fermion quadratures and light modes. The numerical results based on the present day laboratory experiments agree with the obtained analytical results.
关键词： Fabry–Pérot cavity,quantum degenerate Fermi gas,Normal mode splitting,fermionic displacement spectrum,strong coupling regime
更新于2025-09-09 09:28:46