Linewidth of a quantum-cascade laser assessed from its frequency noise spectrum and impact of the current driver

Tombez, Lionel; Schilt, Stéphane; Francesco, J. di; Führer, Thorsten; Rein, Benjamin; Walther, Thomas; Domenico, G. Di; Hofstetter, Daniel; Thomann, P.

doi:10.1007/s00340-012-5005-x

Cited by 41 publications

(47 citation statements)

References 35 publications

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“…The controller incorporates a highly stable thermal regulator that stabilizes the QCL temperature to better than 1 mK, and a low-noise current source capable of delivering up to 600 mA at 20 V compliance voltage or 1 A at 14 V. The current source has a noise spectral density lower than 1 nA/Hz 1/2 at Fourier frequencies higher than 1 kHz and a slightly increasing noise at lower frequency when measured on a pure resistor at similar operating voltage and current as typically used in the QCLs. With the typical cur-rent-tuning coefficient of the QCLs considered in this study (0.2-1 GHz/mA), this noise level enabled us to observe the frequency noise induced in the laser itself, without techni-cal limitation resulting from the current driver [25]. The use of such a low-noise current source was thus a prereq-uisite for the experimental investigation of noise generated within the different laser structures.…”

Section: Methodsmentioning

confidence: 94%

An experimental study of noise in mid-infrared quantum cascade lasers of different designs

et al. 2015

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Section: Methodsmentioning

confidence: 94%

An experimental study of noise in mid-infrared quantum cascade lasers of different designs

et al. 2015

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“…These drivers can deliver a current up to 1 A and have a noise spectral density lower than 1 nA/Hz 1/2 at Fourier frequencies higher than 1 kHz. This feature generally enables accessing the frequency noise inherent to a QCL itself, without technical limitation resulting from the QCL current source [12]. The IH has a nearly ohmic response, as shown in Figure 1b, with an assessed resistance of~9 Ω that is almost independent of temperature.…”

Section: Methodsmentioning

confidence: 99%

Frequency Tuning and Modulation of a Quantum Cascade Laser with an Integrated Resistive Heater

et al. 2016

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Abstract:We present a detailed experimental investigation of the use of a novel actuator for frequency tuning and modulation in a quantum cascade laser (QCL) based on a resistive integrated heater (IH) placed close to the active region. This new actuator is attractive for molecular spectroscopy applications as it enables fast tuning of the QCL wavelength with a minor influence on the optical output power, and is electrically-controlled. Using a spectroscopic setup comprising a low-pressure gas cell, we measured the tuning and modulation properties of a QCL emitting at 7.8 µm as a function of the active region and IH currents. We show that a current step applied to the IH enables the laser frequency to be switched by 500 MHz in a few milliseconds, as fast as for a step of the current in the active region, and limited by heat dissipation towards the laser sub-mount. The QCL optical frequency can be modulated up to~100 kHz with the IH current, which is one order of magnitude slower than for the QCL current, but sufficient for many spectroscopic applications. We discuss the experimental results using a thermal model of the heat transfer in terms of cascaded low-pass filters and extract the respective cut-off frequencies. Finally, we present a proof-of-principle experiment of wavelength modulation spectroscopy of a N 2 O transition performed with a modulation of the IH current and show some potential benefits in comparison to QCL current modulation, which results from the reduced associated amplitude modulation.

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“…The temperature controller stabilizes the QCL temperature at the mK level, which is important for long-term reliability. The current source has a low enough noise level of <1 nA/Hz 1/2 at Fourier frequencies higher than 1 kHz, which enables observing the noise induced in the QCL itself without technical limitation from the driver [10]. Before being implemented in the long-term experiment reported here, the QCL under test has barely been operated during a few hours.…”

Section: Experimental Setup and Methodsmentioning

confidence: 99%

“…Other spectral properties of QCLs are also essential for these applications, such as the frequency noise and associated linewidth. QCLs are known to have a very narrow intrinsic linewidth at the 100-Hz level [9], but they suffer from extra flicker (1/f) noise that significantly broadens the actual linewidth encountered in practice, typically to the megahertz level [10]. Several experimental studies of frequency noise in QCLs were performed in the last years [9], [11]- [14].…”

mentioning

confidence: 99%

Frequency Ageing and Noise Evolution in a Distributed Feedback Quantum Cascade Laser Measured Over a Two-Month Period

Schilt

Tombez

Haller

et al. 2015

IEEE J. Select. Topics Quantum Electron.

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Abstract-We report on the evaluation of the frequency stability of a distributed feedback quantum cascade laser (QCL) at 8 μm that was continuously monitored over a 2-month period using a spectroscopic setup. The QCL was operated in continuous wave mode at room temperature (21.4°C). It was driven by a home-made low-noise controller at a nominal current of ∼600 mA located in the middle of its operation range. Two distinctive behaviors were observed. A monotonous frequency drift of about 1.8 GHz was observed during slightly more than the first month, followed by a stable regime in the second month where the frequency remained within a 100 MHz range. In addition, the electrical flicker noise of the QCL was regularly measured during the same period, and similarly showed two different regimes. The noise regularly decreased at a small rate of about 0.3%/day during the first month, whereas it tends to stabilize during the second month. We believe that an improvement of the QCL contacts over time is responsible for this behavior. After the initial one-month period, the QCL showed a remarkably stable behavior that is beneficial for many applications that require stable long-term operation.Index Terms-Laser noise, laser reliability, laser stability, quantum cascade laser.

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Linewidth of a quantum-cascade laser assessed from its frequency noise spectrum and impact of the current driver

Cited by 41 publications

References 35 publications

An experimental study of noise in mid-infrared quantum cascade lasers of different designs

An experimental study of noise in mid-infrared quantum cascade lasers of different designs

Frequency Tuning and Modulation of a Quantum Cascade Laser with an Integrated Resistive Heater

Frequency Ageing and Noise Evolution in a Distributed Feedback Quantum Cascade Laser Measured Over a Two-Month Period

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