- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[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) - Thermal Noise in Optically Pumped DF-VECSELs
摘要： Over the last decades, the low noise properties of Vertical–External–Cavity Surface–Emitting Lasers (VECSELs) have aroused interest for various applications. The dual–frequency (DF) VECSELs can generate a very low noise RF signal resulting from the beatnote of two orthogonal linear polarizations as sketched in Fig.1(a). For example, the very high spectral purity and class–A operation of DF–VECSELs are of interest for ultrastable atomic clocks [1] or microwave electronics for optically-carried RF signal processing or wide-band RADARs. The sources of noise of optically pumped VECSELs are well identi?ed : (i) the intensity noise induced by the pump through the laser dynamics, (ii) the spontaneous emission contribution, (iii) technical noises such as mechanical vibrations, and (iv) the thermal noise. The two ?rst sources of noise are well modeled and understood. But in [2] a simple second–order low-pass ?lter behaviour is assumed for the thermal contribution to the frequency noise power spectral density (PSD) spectra. Yet, de?ning unequivocally a cut–off frequency is not obvious since different time scales are actually involved. Moreover, this over–simpli?ed model fails at low frequencies in [3] as displayed in Fig.1(b). Indeed, below 200 kHz the slope of the beatnote phase–noise spectrum of a DF–VECSEL at 852 nm obeys a f ?3 scaling law instead of the f ?4 expected behaviour. The aim of the present work is to microscopically model the thermal noise contribution. First, we describe the layers of the optically pumped emitting–surface, which is glued to a Peltier cooler. The heat equations take into account transverse and longitudinal diffusion processes. Assuming a gaussian pro?le for the pump, we obtain the temperature ?eld inside the structure using Hankel transformation formalism and we investigate the transient thermal response. The pump intensity ?uctuations induce heat ?uctuations inside the structure leading to changes of the refractive index and the material thermal–expansion, which are responsible for frequency ?uctuations of the laser mode. We ?nd an analytical expression of the frequency noise PSD induced by these thermo-optic effects, which allows to model the beatnote phase noise PSD of DF-VECSELs. We ?nd a very good agreement with the f ?3 slope of the experimental datas and we evidence the fundamental thermal ?uctuations contribution at room temperature. Such thermodynamics ?uctuations were already investigated for VCSEL structures in [4], starting from a stochastic heat equation. We extend it to a full study of the frequency noise PSD spectrum for DF-VECSELs. We obtain a fully analytical expression and discuss its validity.
关键词： Thermal noise,frequency noise PSD,thermal fluctuations,optically pumped,DF-VECSELs
更新于2025-09-16 10:30:52
-
Wavelength and pump-power dependent nonlinear refraction and absorption in a semiconductor disk laser
摘要： We characterize both nonlinear refraction and absorption in a vertical-external-cavity surface-emitting laser (VECSEL) as a function of pump irradiance over the whole range of lasing wavelengths. We observe an approximately linear decrease in magnitude for both nonlinear refraction and nonlinear absorption with optical pumping when the thermally induced shift of the lasing wavelength is considered. Our results are of particular significance for understanding self-modelocking of VECSELs which might be driven by nonlinear lensing.
关键词： mode-locked semiconductor lasers,Z-scan,Nonlinear refractive index,VECSELs
更新于2025-09-16 10:30:52
-
[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