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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) - Rate Equation Modeling of Interband Cascade Lasers
摘要： Interband cascade lasers (ICLs) are power-efficient mid-infrared laser sources for applications in sensing of numerous molecules and in free-space optical communications. The static performances of ICLs including the lasing threshold and the output power have been significantly improved since its first demonstration by R. Yang [1]. GaSb-based ICLs have optimal performance in the spectral range of 3-4 μm, which is hard to reach for the quantum cascade laser counterpart [2]. This work proposes a rate equation model for studying dynamical characteristics of ICLs including the intensity modulation (IM) response, the relative intensity noise (RIN), and the frequency noise (FN). Taking into account carrier dynamics in the W-shape active region while ignoring those in the electron and hole injectors [3], the rate equations for the carrier number N, the photon number S, and the phase φ of the electric field read. Based on the standard small-signal analysis of the above rate equations, we obtain analytical formulas for IM response, RIN, and FN, respectively (not shown in this paper). The inset of Fig. 1(a) shows that ICLs exhibit an underdamped resonance peak in the IM response at a low pump current, and the modulation bandwidth increases with increasing pump current as conventional laser diodes. Figure 1(a) proves that more gain stages are desirable for enhancing the modulation bandwidth of ICLs. The inset of Fig. 1(b) shows that the RIN is raised at the resonance frequency, while a small stage number reduces the RIN in the whole spectral range. Figure 1(b) demonstrates that the RIN at the low-frequency range (<1.0 GHz) increases nonlinearly with the gain stage number. The inset of Fig. 1(c) shows that the FN of ICLs is raised at the resonance frequency, while a small stage number reduces the FN in the whole spectral range as well. The intrinsic spectral linewidth of ICLs in Fig. 1(c) is obtained from the low-frequency FN level. It is found that the intrinsic linewidth linearly increases with the gain stage number, which is consistent with the derived analytical formula. In summary, we theoretically prove that a large gain stage number is desirable for enhancing the modulation bandwidth, while a small stage number is favorable to reduce both the RIN and the FN/linewidth of ICLs.
关键词： Interband cascade lasers,rate equation model,frequency noise,intensity modulation,relative intensity noise
更新于2025-09-12 10:27:22
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High energy and high frequency electro-optic Q-switching laser with alternating output of energy amplitude
摘要： The high energy and high frequency electro-optic Q-switching laser with alternating output of energy amplitude was the first reported by the temporal delay of pulse energy in 1064 nm laser. The experimental schematic of the output 1064 nm laser with different trigger time were obtained when turn on the Q-switch on the 60 μs. When turn on the Q-switch on the 71 μs, the pulse energy of 1064 nm is distributed in a “high-low” pulse sequence: the pulse energy of the 1st was higher than 2nd, and the 2nd pulse energy was lower than the 3rd is formed repeatedly, when turn on the Q-switch on the 48 μs, the output process of the pulse laser is reversed. To the best of our knowledge, it is the first time to report the high energy and high frequency electro-optic Q-switching laser with alternating output of energy amplitude. In experiment a repetition rate of 100 kHz with a pulse width of 13 ns was achieved when the pump power was 24 J and the charging voltage is 650 V, the total output power of 0.8 J was obtained and the conversion efficiency is 0.3%. And the result of the photon density distributions and the inverse population by numerical calculations are basically agree with the experiment result.
关键词： Alternating output of energy amplitude,Temporal delay,Rate equation model,High energy and High frequency
更新于2025-09-12 10:27:22