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Effect of cold finger temperature on optical pulse modulation characteristics in a 2.59 terahertz quantum cascade laser
摘要： Terahertz (THz) frequency sources such as quantum cascade lasers (QCLs) offer a variety of new applications in far-infrared frequency bands. For better understanding of their behavior, a device-specific modeling approach is used to predict the optical output power under current modulation and chip temperature. This letter reports the numerical simulation of gain switching to evaluate temperature dependence for short pulse generation in QCLs. Modified rate equations are used for self-consistent computation of emitted THz optical power from QCLs. The device emits at 116 μm and is driven by various inputs such as haversine, tangential hyperbolic and square electrical pulses. From the simulation it is evident that the square input pulse requires the least magnitude current (0.83 A) at 15 K to generate pulses with minimum full width half maximum (FWHM). Moreover, when the peak amplitude of the square input signal is 1.01 A, it generates optical pulses with the least FWHM of 19.42 ps at 45 K. In the case of the haversine input with peak amplitude of 1.8A, a peak power of 27.86 mW is generated at 15 K.
关键词： cold finger temperature,rate equation model,numerical simulation,quantum cascade lasers,full width half maximum,gain switching,optical short pulses
更新于2025-09-23 15:19:57
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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) - Optical Frequency Comb Generation from Semiconductor Lasers using Optical Injection and Pulsed Gain Switching
摘要： An Optical Frequency Comb (OFC) Generator is a laser source emitting a coherent radiation with an equally spaced group of optical frequencies. OFCs have been used in numerous fields, such as optical communications, RF photonics and infrared spectroscopy. Relatively low repetition rate OFCs (100-1000 MHz) are especially suited for dual comb spectroscopic applications. Low repetition rate OFCs from Gain-Switched (GS) semiconductor lasers using sinusoidal excitation have been reported for spectroscopic applications. On the other hand, the generation of ultra-short optical pulses by pulsed excitation GS has been demonstrated, but as far as we know, it has not been used for OFC generation. In this work, we consider pulsed GS in combination with optical injection (OI) to generate low repetition rate OFCs, and we demonstrate a high performance in terms of noise, flatness and bandwidth. The OFC generator is based on a master-slave configuration. The Slave Laser (SL), a Discrete Mode Laser (DML), is driven in GS operation using a combination of two signals: a bias current and a square signal provided by a pulse pattern generator, with different duty cycles and driving conditions. High-resolution spectra were analyzed with a Brillouin Optical Spectrum Analyzer (BOSA).
关键词： Optical Frequency Comb,Pulsed Gain Switching,Semiconductor Lasers,Dual Comb Spectroscopy,Optical Injection
更新于2025-09-16 10:30:52
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Mode-locking and self-mode-locking-like operation in a resonantly pumped gain-switched Tm-doped fiber laser
摘要： Mode-locking and mode-locking-like operation in a fast gain-switched Tm-doped fiber laser have been investigated experimentally. Applying a SESAM mirror, stable gain-switched and regular mode-locked pulses at a wavelength of ～2μm are reported. The repetition rates of the gain-switched pulses and mode-locked sub-pulses are 50 kHz and 111 MHz, respectively. The duration of sub-pulses recorded within one gain-switched pulse envelope is ～110 ps. Besides, in the same laser system configuration, it has been found that self-starting mode-locked resembling pulses, attributed to mode beating, can be generated. To the best of our knowledge, it is the first report on a gain-switched fiber laser where both modes of operation have been demonstrated.
关键词： Fiber laser,Mode-locking,Thulium-doped fiber,Gain-switching
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) - Analysis of Optical Frequency Comb Generation in Gain-Switched Semiconductor Lasers
摘要： An Optical Frequency Comb (OFC) Generator is a laser source emitting an equally spaced group of optical tones. These types of optical sources have found application in different fields, such as spectroscopy [1] and optical communications [2]. Among the three main techniques for generating OFCs from semiconductor lasers, namely gain switching, electro-optic modulation and mode-locking, gain switching (GS) has attracted attention due to the simple selection of the repetition frequency and its easy implementation and low cost. We present here an exhaustive and systematic comparative analysis of the OFC generation using GS in semiconductor lasers. We have used a theoretical model, based on three stochastic differential equations that include non-linear saturation and Langevin noises, in order to simulate the experimental results. The experimental and simulated response has been studied in order to identify the main physical processes involved in the generation of GS OFC. An experimental characterization, based on RIN spectra measurements [5], was used to extract the parameters of the model. The OFC generator consists on a Discrete Mode Laser (DML), which is driven in GS operation using a bias current and a sinusoidal signal. High-resolution spectra were measured with a Brillouin Optical Spectrum Analyzer (BOSA).
关键词： Optical Frequency Comb,Spectroscopy,Optical Communications,Semiconductor Lasers,Gain Switching
更新于2025-09-12 10:27:22
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Numerical and Experimental Analysis of Optical Frequency Comb Generation in Gain-Switched Semiconductor Lasers
摘要： We have performed a systematic experimental and simulation analysis of the optical frequency combs generated by gain-switching single mode laser diodes, either free-running or subjected to optical injection. The simulations have been produced with a dynamical model consisting of three rate equations that include stochastic noise terms. The model parameters have been extracted from experiments. An exhaustive comparison between the simulated and the experimental temporal profiles and optical spectra generated under a wide range of switching and optical injection conditions has been performed. The excellent quantitative agreement found in the entire range of the explored operating conditions supports the validity of the model for the analysis of the comb generation mechanisms. The detailed maps generated provide guidelines for selecting suitable operating conditions for specific comb characteristics.
关键词： optical frequency combs,Semiconductor lasers,rate equations,optical injection,gain switching
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - Characteristics of 1.3μm Electrically Pumped InAs/AlGaInAs Quantum Dot Lasers on (001) Silicon
摘要： We present preliminary characterization results of the first InAs/InAlGaAs/InP 1.3μm quantum dots (QDs) laser directly grown on (001) silicon. A threshold current density of 1.05 kA/cm2 under pulsed current injection has been obtained. A 50 ns width optical pulse was observed under gain-switching measurement.
关键词： InAs-InAlGaAs-InP QDs,1.3μm lasers,gain-switching
更新于2025-09-11 14:15:04