Effects of self-mixing interference on gain-coupled distributed-feedback lasers

Zhou, Junping; Wang, Ming

doi:10.1364/opex.13.001848

Cited by 13 publications

(4 citation statements)

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“…where h] l is the photon energy and R is the reflectivity of the output facet. We can then obtain the self-mixing power signal by the formula ΔP P l − P l0 (17) where P l and P l0 are the optical power with and without optical feedback, respectively. It should be also noted that we assume the linewidth enhancement factor α 0 for THz QCLs [5].…”

Section: Theoretical Model Of Smi In Thz Complex-coupled Dfb-qclsmentioning

confidence: 99%

“…From this point of view, some early studies investigated the properties of SMI in index-coupled diode lasers using the coupled wave theory, and the results show that the cosine-like self-mixing signal is similar to that from a single-mode FP laser [15,16]. Furthermore, some studies also have shown that SMI sensors based on gain-coupled DFB lasers exhibit high accuracy [17]. However, a DFB laser with a grating etched into its upper cladding layer has an increased waveguide loss through the top contact layer, and this may in turn decrease its performance [18].…”

Section: Introductionmentioning

confidence: 99%

“…The Lang-Kobayashi (L-K) equations are generally employed to study the dynamical behavior of SMI in FP-QCLs. However, the L-K equations cannot be simply applied to DFB-QCLs under optical feedback, despite the fact that several studies have used modified L-K equations to this end [17]. Here, we use the coupled wave theory to describe the mode-coupling phenomenon and calculate the emission power of complex-coupled THz DFB-QCLs under SMI using the multi-mode rate equation method.…”

Section: Introductionmentioning

confidence: 99%

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Self-Mixing Signal Characteristics of Complex-Coupled Distributed-Feedback Terahertz Quantum-Cascade Lasers

Wang

Chu

et al. 2021

Front. Phys.

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Self-mixing interference (SMI) in terahertz quantum cascade lasers (THz QCLs) is one of the significant approaches for coherent THz imaging and sensing techniques. Here, the output characteristics of SMI in distributed feedback (DFB) THz QCLs from the index-to the gain-coupling regimes are studied using the coupled wave theory and the multi-mode rate equation method. A mode hopping phenomenon is found to occur when the DFB coupling factor changes from index-coupling to gain-coupling, and the characteristics of the self-mixing signals of DFB-QCLs change greatly with this mode hopping. With the modulus of the coupling factor fixed and its argument varied from 0 to π/2, an extreme point of the self-mixing frequency and power signals of DFB-QCLs is found at π/9 due to the mode hopping. For index-coupling dominated DFB-QCLs, both the varying ranges of the self-mixing frequency signals and amplitudes of power signals increase with increasing DFB coupling factor argument. For gain-coupling dominated DFB-QCLs, with increasing argument value, the amplitude of the self-mixing power signal increases, but the varying range of the self-mixing frequency signal decreases. With the argument of the coupling factor fixed, we also found that the varying ranges of the self-mixing frequency signals decrease with increasing modulus for both index-coupling dominated and gain-coupling dominated DFB-QCLs. For index-coupling dominated DFB-QCLs, the amplitudes of the self-mixing power signals decrease with increasing modulus; however, the amplitudes of the self-mixing power signals of gain-coupling dominated DFB-QCLs increase. With the argument of the coupling factor fixed, for index-coupling dominated DFB-QCLs, we found that the varying ranges of the self-mixing frequency signals and amplitudes of power signals decrease with the increasing modulus. For gain-coupling dominated DFB-QCLs, with the coupling factor modulus increasing, the varying ranges of the self-mixing frequency signals decrease, however, the amplitudes of the self-mixing power signals increase. These results may help with the application of DFB-QCLs to self-mixing interferometers.

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Section: Theoretical Model Of Smi In Thz Complex-coupled Dfb-qclsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Self-Mixing Signal Characteristics of Complex-Coupled Distributed-Feedback Terahertz Quantum-Cascade Lasers

Wang

Chu

et al. 2021

Front. Phys.

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“…Despite the isolation stage of the system, very low power light is sufficient to cause self-mixing within DFB lasers. 5 The self-mixing of the laser made the vibrometer system sensitive to displacement of the target rather than velocity. Therefore there was a greater error in the demodulated velocity signal at low velocities compared with the demodulated velocity signal obtained from higher velocities of the target.…”

Section: Figure 2: Lens-target Assembly With Excited Target Facementioning

confidence: 99%

Fiber Optic Vibrometer Measuring Ballistic Shock

Thomas¹,

Weis²

2009 GSW Proceedings

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An interferometric fiber optic vibrometer designed to measure vibrations caused by ballistic impacts was designed, constructed and tested. The system employs a Mach-Zehnder interferometer with a passive stabilization design scheme. By eliminating high-speed electronic circuitry, the transient response of the system is improved, and the cost and complexity of the system is reduced. The vibrometer was designed to be sensitive to vibrations at velocities of 1m/s.

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