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Author Ekstrom H.; Karasik B. S.; Kollberg E.L.; Yngvesson K.S. openurl 
  Title Conversion Gain and Noise of Niobium Superconducting Hot-Electron-Mixers Type Journal Article
  Year 1995 Publication IEEE Trans. Microw. Theory Techn. Abbreviated Journal  
  Volume 43 Issue (up) Pages 938-947  
  Keywords  
  Abstract A study has been done of microwave mixing at 20 GHz using the nonlinear (power dependent) resistance of thin niobium strips in the resistive state. Our experiments give evidence that electron-heating is the main cause of the nonlinear phenomenon. Also a detailed phenomenological theory for the determination of conversion properties is presented. This theory is capable of predicting the frequency-conversion loss rather accurately for arbitrary bias by examining the I-V-characteristic. Knowing the electron temperature relaxation time, and using parameters derived from the I-V-characteristic also allows us to predict the -3-dB IF bandwidth. Experimental results are in excellent agreement with the theoretical predictions. The require ments on the mode of operation and on the film parameters for minimizing the conversion loss (and even achieving conversion gain) are discussed in some detail. Our measurements demon-strate an intrinsic conversion loss as low as 1 dB. The maximum IF frequency defined for -3-dB drop in conversion gain, is about 80 MHz. Noise measurements indicate a device output noise temperature of about 50 K and SSB mixer noise temperature below 250 K. This type of mixer is considered very promising for use in low-noise heterodyne receivers at THz frequencies.  
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  Call Number RPLAB @ atomics90 @ Serial 964  
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Author Khosropanah P.; Baryshev A.; Zhang W.; Jellema W.; Hovenier J.N.; Gao G.R.; Klapwijk T.M; Paveliev D.G.; Williams B.S.; Kumar S.; Hu Q.; Reno J.L.; Klein B.; Hesler J.L. openurl 
  Title Phase-locking of a 2.7-THz quantum cascade laser to a microwave reference Type Journal Article
  Year 2009 Publication Optics Letters Abbreviated Journal  
  Volume 34 Issue (up) Pages 2958-2960  
  Keywords  
  Abstract We demonstrate the phase locking of a 2.7 THz metal–metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier chain (X12) from a

microwave synthesizer at ~ 15 GHz. Both laser and reference radiations are coupled into a bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. The spectral analysis of the beat signal con-firms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range.
 
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  Call Number RPLAB @ atomics90 @ Serial 966  
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Author Baryshev A.; Hovenier J.N.; Adam A.J.L.; Kašalynas I.; Gao J.R.; Klaassen T.O.; Williams B.S.; Kumar S.; Hu Q.; Reno J.L. openurl 
  Title Phase locking and spectral linewidth of a two-mode terahertz quantum cascade laser Type Journal Article
  Year 2006 Publication Physics Letters Abbreviated Journal  
  Volume 89 Issue (up) Pages  
  Keywords  
  Abstract We have studied the phase locking and spectral linewidth of an ~ 2.7 THz quantum cascade laser by mixing its two lateral lasing modes. The beat signal at about 8 GHz is compared with a microwave eference by applying conventional phase lock loop circuitry with feedback to the laser bias current. Phase locking has been demonstrated, resulting in a narrow beat linewidth of less than 10 Hz. Under requency stabilization we find that the terahertz line profile is essentially Lorentzian with a minimum linewidth of ~ 6.3 kHz. Power dependent measurements suggest that this linewidth does not approach the Schawlow-Townes limit.  
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  Call Number RPLAB @ atomics90 @ Serial 967  
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Author Hovenier J.N.; Adam A.J.L.; Kašalynas I.; Gao J.R.; Klaassen T.O.; Baryshev A.; Williams B.S.; Kumar S.; Hu Q.; Reno J.L. openurl 
  Title Phase-locking on the beat signal of a two-mode 2.7 terahertz metal-metal quantum cascade laser Type Conference Article
  Year 2006 Publication Proc. Symp. IEEE/LEOS Benelux Chapter Abbreviated Journal  
  Volume Issue (up) Pages 125-128  
  Keywords  
  Abstract We have studied the linewidth and phase-locking of a 2.7 THz quantum cascade laser by using a superconducting bolometer mixer. The 8 GHz beat signal is compared with a microwave reference with a feedback to the laser bias current. Phase locking has been demonstrated, resulting in an extremely narrow beat linewidth of less than 10 Hz. Under frequency-stabilization conditions we find that the line profile is virtually Lorentzian with a long-term minimum linewidth of the THz modes of about 6.3 kHz. Temperature dependent measurements suggestthat this linewidthdoes not approach the Schawlow-Townes limit.  
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  Call Number RPLAB @ atomics90 @ Serial 968  
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Author Irimajiri, Y.; Kumagai, M.; Morohashi, I.; Kawakami, A.; Nagano, S.; Sekine, N.; Ochiai, S.; Tanaka, S.; Hanado, Y.; Uzawa, Y.; Hosako, I. doi  isbn
openurl 
  Title Phase-locking of a THz-QCL using a Low Noise HEB mixer, and a Frequency-comb as a Reference Type Conference Article
  Year 2014 Publication 39th Int. Conf. IRMMW-THz Abbreviated Journal 39th Int. Conf. IRMMW-THz  
  Volume Issue (up) Pages 1-2  
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  Abstract We have developed a phase-locking system of a 3.1THz QCL (Quantum Cascade Laser) using a low noise hot electron bolometer mixer (HEBM) and a THz reference. The THz reference was generated by photomixing two optical modes of a frequency comb. The THz-QCL and HEBM devices are fabricated in our laboratory. A line width of the phase-locked QCL of narrower than 1Hz was achieved.  
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  ISSN ISBN 978-1-4799-3877-3 Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number RPLAB @ atomics90 @ Serial 969  
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