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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) - Tailoring Single-Frequency VECSELs for Quantum Technology Applications
摘要： Many quantum technology applications, such as quantum information processing, precision metrology, and atomic clocks, rely on lasers at many different wavelengths with demanding characteristics in terms of power, linewidth, beam quality, and intensity noise. These lasers are typically used to detect or change the quantum states of neutral atoms and ions. Besides the need for precisely defined features fitting a specific atom/ion system, there is an increasing need to make such lasers more affordable, as well as easier to use and tailor, in order to ensure faster transit from lab to real applications. Vertical-External-Cavity Surface-Emitting Lasers (VECSELs, aka. OPSLs or SDLs) are optically pumped semiconductor lasers that combine the benefits of semiconductor quantum well -lasers; the wavelength versatility and the wide pump absorption bandwidth, with the benefits of diode-pumped solid-state lasers; the high output power and excellent beam quality. The external cavity geometry of VECSELs enables the insertion of intracavity wavelength selective elements for tunable single-frequency operation, and the insertion of nonlinear crystals for efficient intracavity frequency conversion. These features make VECSELs very promising candidates to address the needs of quantum technology and other high impact applications. We present compact turnkey single-frequency VECSELs tailored for quantum technology applications, for generation and manipulation of trapped ions for quantum computing. Our previous demonstration was focused on VECSEL-based systems at 279.6 nm for Doppler cooling and at 285.3 nm for photoionization of magnesium ions. Here, we focus on wavelength extension and tailoring the single-frequency operation for use with several other promising ions, such as beryllium at 313 nm and 235 nm. We present very recent results of Watt-level single-frequency emission at challenging 1252 nm and 940 nm wavelengths, which are prerequisites for high power emission at 313 nm and 235 nm, as well as recent developments on the laser platform. We believe that VECSELs can potentially replace many of the laser systems currently in use and enable new quantum technology applications.
关键词： single-frequency lasers,VECSELs,quantum computing,quantum technology,trapped ions
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) - Determination of the Residual Amplified Spontaneous Emission in Single-Mode Semiconductor Optical Amplifiers
摘要： The Master-Oscillator-Power-Amplifier (MOPA) is a laser light source best suited to provide high power, stable frequency, and narrow linewidth emission. In state-of-the-art MOPA systems, semiconductor optical amplifiers (SOAs) with single-mode lateral waveguides provide a compromise between the demands for high power on one side and excellent beam quality and small astigmatism of the optical mode on the other. The amplified spontaneous emission (ASE) in SOAs remains a limiting factor for the deployment of the MOPA systems in quantum technology applications. The presence of ASE reduces the carrier density and hence the device efficiency, increases the noise in the output signal, and adds incoherent background radiation that is critical, for example, for atom interferometry applications. It is therefore important to understand the dependence of the ASE on the design and operating conditions of an SOA in detail in order to develop SOAs optimized for applications that require spectrally very pure radiation. In this work, the coherent and the residual ASE power of ridge waveguide (RW) SOAs are experimentally determined as a function of the seed power (optical power at the input of the SOA) and the SOA current. The experiment provides essential information about the suppression of the ASE background and the saturation behaviour of the optical amplifier. The measurement setup is depicted in Fig. 1 (a). The seed laser (ECDL, TE-polarized at 871 nm) is operated far above its threshold to avoid amplification of the spontaneous emission of the seed laser by the SOA. An acousto-optic modulator (AOM) is used to set the seed power. The laser beam is then fed into the 6 mm long SOA. A non-polarizing beam splitter (BS) cube divides the output beam into two parts. One part (reference beam) is detected using a power meter (PM). The spectrum of the second part is recorded using an Advantest Q8347 optical spectrum analyser (OSA). The measured data is analysed using the correlation between optical power measured with the power meter and the optical spectrum. The ASE power is reconstructed from the remaining ASE (fitted) spectrum after removing the coherent part. Fig. 1(b) shows the measured total output, ASE and coherent powers retrieved from the spectrum as a function of the seed power. The measured quantities in Fig. 1(b) are compared to theoretical values which are calculated using a SOA model similarly as described in [2]. The carrier-density dependent spectra of the gain and the spontaneous emission are obtained from a microscopic model taking into account the waveguide structure [3]. The comparison shows good qualitative agreement between theory and measurement. We show how the experimental findings are used to validate and calibrate the model and how the model can be applied to compare the performance (coherent power, ASE background, saturation behaviour) of SOAs at different seed powers, injection current setting, different lengths or different lateral geometries.
关键词： ridge waveguide SOAs,semiconductor optical amplifiers,Master-Oscillator-Power-Amplifier,quantum technology applications,amplified spontaneous emission
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) - Controllable Photon-Pair Spectral Correlations
摘要： Photon-pair states, whether spectrally correlated or separable, can all be very useful in quantum technology applications. For example, the former are used for improving the security of quantum key distribution, whilst the latter are the backbone in heralded single photon sources. It has been shown that the amount of spectral correlations is well-described by the shape of the Joint Spectral Amplitude function (JSA), which mostly depends on the relative group velocity relation between the pump, signal and idler photons within the source medium [1]. Here, we report on a photon-pair source whose states can be controlled from separable to spectrally entangled. The source is based on four-wave mixing nonlinear effect within a gas-filled hollow-core photonic crystal fiber (HCPCF). It combines three important properties: (1) Raman-free generation thanks to the use of a noble gas and to a minute overlap with silica within the hollow-core [2]; (2) strong efficiency nonlinear medium and (3) a high versatility in the phase-matching conditions thanks to the fiber microstructuration and gas pressure tunability. The inhibited-coupling HCPCF (see Fig.1a) filled with xenon, was designed to operate at wavelengths that are convenient for heralded single photon sources; the idler lies in the telecom wavelength range (~ 1545 nm), while the signal wavelength is in the range of atomic transitions and Silicon single photon detectors (~ 778 nm). More importantly, we show how the multiband dispersion profile (see Fig. 1b) of such medium allows to tailor phase- and group velocity relations and possibly at any given wavelength from the UV to infrared [3]. We demonstrate experimentally an active control over the generated photon spectral-correlation that allows spectrally entangled and factorable states to be obtained within the same device (examples in Fig. 1c). More specifically, a gallery of different JSI, including exotic shape, is measured by tuning various parameters: gas pressure, pump spectral FWHM, spectral chirp and pump spectral envelope. Such a versatile photon-pair source can target both applications requiring factorable (heralded single photon) and correlated states (spectral entanglement) and paves the way to spectro-temporal mode encoding [4]. Furthermore, the photon-pair state is generated over an unprecedented tunable frequency-range that span well over tens of THz. We will present complete theoretical and experimental results demonstrating the full capacity of this platform to generate photon pair with controllable spectral properties.
关键词： photon-pair states,hollow-core photonic crystal fiber,spectral correlations,quantum technology,spectral entanglement,four-wave mixing
更新于2025-09-11 14:15:04
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Polarization Entanglement by Time-Reversed Hong-Ou-Mandel Interference
摘要： Sources of entanglement are an enabling resource in quantum technology, and pushing the limits of generation rate and quality of entanglement is a necessary prerequisite towards practical applications. Here, we present an ultrabright source of polarization-entangled photon pairs based on time-reversed Hong-Ou-Mandel interference. By superimposing four pair-creation possibilities on a polarization beam splitter, pairs of identical photons are separated into two spatial modes without the usual requirement for wavelength distinguishability or noncollinear emission angles. Our source yields high-fidelity polarization entanglement and high pair-generation rates without any requirement for active interferometric stabilization, which makes it an ideal candidate for a variety of applications, in particular those requiring indistinguishable photons.
关键词： photon pairs,quantum technology,Hong-Ou-Mandel interference,polarization entanglement
更新于2025-09-10 09:29:36