Publications (7)16.52 Total impact
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Article: Subkilohertz linewidth room-temperature mid-infrared quantum cascade laser using a molecular sub-Doppler reference.
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ABSTRACT: We report on the narrowing of a room-temperature mid-IR quantum cascade laser by frequency locking it to a CO<sub>2</sub> sub-Doppler transition obtained by polarization spectroscopy. A locking bandwidth of 250 kHz has been achieved. The laser linewidth is narrowed by more than two orders of magnitude below 1 kHz, and its absolute frequency is stabilized at the same level.Optics Letters 12/2012; 37(23):4811-3. · 3.40 Impact Factor -
Article: Measuring frequency noise and intrinsic linewidth of a room-temperature DFB quantum cascade laser.
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ABSTRACT: The frequency-noise power spectral density of a room-temperature distributed-feedback quantum cascade laser emitting at λ = 4.36 μm has been measured. An intrinsic linewidth value of 260 Hz is retrieved, in reasonable agreement with theoretical calculations. A noise reduction of about a factor 200 in most of the frequency interval is also found, with respect to a cryogenic laser at the same wavelength. A quantitative treatment shows that it can be explained by a temperature-dependent mechanism governing the transport processes in resonant tunnelling devices. This confirms the predominant effect of the heterostructure in determining shape and magnitude of the frequency noise spectrum in QCLs.Optics Express 09/2011; 19(19):17996-8003. · 3.59 Impact Factor -
Article: High-Performance Quantum Cascade Lasers With Single Phonon-Continuum Depopulation Structures
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ABSTRACT: We report high performance λ~8.6 μm m quantum cascade lasers based on 5 quantum well single phonon-continuum (SPC) depopulation scheme, grown by metal organic vapor-phase epitaxy. Devices with SPC depopulation structures exhibit high device performances in pulsed and continuous wave (CW) operation due to a large dipole matrix element (3.0 nm) and short depopulation time (0.22 ps). A 4 mm-long, 8 μm-wide, high reflective (HR)-coated buried-hetero-structure laser with 33 cascade stages, for active region, demonstrates a high output power of 313 mW, a threshold current density of 1.35 kA/cm<sup>2</sup>, and slope efficiency of 547 mW/A at 30°C in CW operation. The maximum CW lasing temperature of the device is observed to be 120°C. Furthermore, by using a higher number of cascade stages (N=70) in a 4 mm-long, 22 m-wide, HR-coated ridge laser, a high peak power of 6.3 W is obtained together with a high wall-plug efficiency (WPE) of 10.8%, a slope efficiency of 2.7 W/A, and a threshold current density of 0.76 kA/cm<sup>2</sup> in pulsed operation at 300 K. The measured WPE of over 10% at room temperature is close to the theoretical values.IEEE Journal of Quantum Electronics 06/2010; · 1.88 Impact Factor -
Article: Linewidth enhancement factor of quantum cascade lasers with single phonon resonance-continuum depopulation structure on Peltier cooler
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ABSTRACT: The linewidth enhancement factor (alpha-factor) of a commercially available 6.1 mum InGaAs/InAlAs distributed-feedback quantum cascade laser capable of continuous-wave operation with a Peltier cooler and its current dependence were investigated. alpha tended to increase slowly with an increase in current. alpha, probably affected by detuning, was still smaller than that of conventional 1.55 mum semiconductor laser diodes.Electronics Letters 12/2009; · 0.96 Impact Factor -
Article: Theory of the Intrinsic Linewidth of Quantum-Cascade Lasers: Hidden Reason for the Narrow Linewidth and Line-Broadening by Thermal Photons
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ABSTRACT: We have developed a theory of the intrinsic linewidths of laser output of single-mode quantum-cascade (QC) lasers in mid-infrared and terahertz (THz) ranges. In the theoretical treatment, the concept of an effective coupling efficiency of spontaneous emission, given by a fractional rate of spontaneous emission coupled into a lasing mode to total nonlasing relaxation, is introduced to clarify a hidden reason for the narrowness of the linewidths. A narrow linewidth (12-kHz) reported with a frequency-stabilized 8.5- distributed-feedback QC laser is successfully interpreted in terms of an extremely small effective coupling efficiency of spontaneous emission, caused by ultrafast nonradiative scatterings. The present theory predicts the presence of a minimum ldquolinewidth floorrdquo in a high-injection-current region and the independence of linewidth on detuning between gain-peak and emission wavelengths. The theoretical treatment is expanded to derive the further modified Schawlow-Townes formula including the line-broadening by black body radiation in a THz QC laser. The linewidth of a THz QC laser is predicted to be considerably broadened by black body radiation.IEEE Journal of Quantum Electronics 02/2008; · 1.88 Impact Factor -
Article: Relative intensity noise measurements of 5 μm quantum cascade laser and 1.55 μm semiconductor laser
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ABSTRACT: The magnitude of the relative intensity noise (RIN) of a 5 mum distributed-feedback quantum cascade laser (DFB-QCL) was compared with a conventional 1.55 mum DFB laser diode (LD). The RIN for the DFB-QCL at a frequency of 1 MHz was 157 dBm at 10 mW light output, about 5 dB higher than that of the DFB-LD, which could almost be fully explained by the semi-classical noise model. The resonant tunnelling induced noise, which might be a cause of the RIN degradation, was not observed.Electronics Letters 02/2008; · 0.96 Impact Factor -
Article: Room temperature, continuous-wave operation of quantum cascade lasers with single phonon resonance-continuum depopulation structures grown by metal organic vapor-phase epitaxy
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ABSTRACT: We propose a new quantum-cascade laser structure with single phonon resonance-continuum depopulation and demonstrate room temperature, continuous-wave operation of the proposed 7.9 μm quantum-cascade laser. The laser grown by metal organic vapor-phase epitaxy emits a cw output power of 36 mW at 30 °C, exhibiting a threshold current density of 2.23 kA/cm2. The cw operation is reported for higher temperatures up to slightly above 60 °C. The proposed structure may lead to a successful commercial mass production of the lasers.Applied Physics Letters 10/2007; 91(14):141121-141121-3. · 3.84 Impact Factor
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Institutions
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2008–2012
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HAMAMATSU Photonics K.K.
Hamamatsu, Shizuoka-ken, Japan
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