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  • 1
    Electronic Resource
    Electronic Resource
    Coherent millimeter-wave generation by heterodyne conversion in low-temperature-grown GaAs photoconductors (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 1480-1484 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An analysis has been carried out of optical heterodyne conversion with an interdigitated-electrode photomixer made from low-temperature-grown (LTG) GaAs and pumped by two continuous-wave, frequency-offset pump lasers. The analytic prediction is in excellent agreement with the experimental results obtained recently on a photomixer having 1.0-μm-wide electrodes and gaps. The analysis predicts that a superior photomixer having 0.2-μm-wide electrodes and gaps would have a temperature-limited conversion efficiency of 2.0% at a low difference frequency, 1.6% at 94 GHz, and 0.5% at 300 GHz when connected to a broadband 100 Ω load resistance and pumped at hν=2.0 eV by a total optical power of 50 mW. The predicted 3-dB bandwidth (193 GHz) of this photomixer is limited by both the electron-hole recombination time (0.6 ps) of the LTG-GaAs material and the RC time constant (0.5 ps) of the photomixer circuit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353222
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  • 2
    Electronic Resource
    Electronic Resource
    Electrical, crystallographic, and optical properties of ArF laser modified diamond surfaces (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2295-2297 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pulses of 193 nm radiation from an ArF laser with energies exceeding 0.5 J/cm2 have been shown to modify 40–60 nm thick layers of {100} and {110} oriented diamond surfaces. These layers exhibit highly anisotropic electrical and optical properties which have principal in-plane axes along the 〈110〉 directions. The minimum resistance is (4–10)×10−4 Ω cm, and minimum in the optical transmittance and maximum in the reflectance occur when the electric field vector of the incident polarized light is aligned along the low resistance direction. Transmission electron microscopy indicates that the modified layer primarily consists of unidentified graphite-like carbon phases embedded in diamond. The first-order electron diffraction spots correspond to lattice spacings of 0.123, 0.305, and 0.334 nm. The modified layer is stable at 1800 °C, forms ohmic contacts to type IIb diamond, and supports epitaxial diamond growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102042
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  • 3
    Electronic Resource
    Electronic Resource
    Coherent detection with a GaAs/AlGaAs multiple quantum well structure (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1513-1515 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A GaAs/AlGaAs multiple quantum well (MQW) structure has been investigated as a coherent detector using a CO2-laser local oscillator (LO). At an operating temperature of 77 K, an LO power of 10 mW, an LO wavelength of 10.2 μm, and a bias voltage of 2.0 V, a 150-μm-diam detector displayed an external quantum efficiency η0 of 11% and a 3-dB electrical bandwidth BIF of 1.5 GHz. Under the same conditions the noise-equivalent power density (NEPHET/Δf) at an intermediate frequency of 1.5 GHz was 5.5×10−19 W/Hz, which is within 50% of the photon-noise limit for this detector. A 75-μm-diam detector with a lower-capacitance bond wire was found to have a BIF of 8 GHz and an NEPHET/Δf of 4.1×10−19 W/Hz with only 2.5 mW of LO power. The photoelectron lifetime in the MQW structure at 77 K was estimated to be 2.5 ps corresponding to an intrinsic detector bandwidth of 64 GHz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108624
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  • 4
    Electronic Resource
    Electronic Resource
    Milliwatt output levels and superquadratic bias dependence in a low-temperature-grown GaAs photomixer (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3311-3313 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A cw output power up to 0.8 mW is obtained from a low-temperature-grown (LTG) GaAs, 0.3 μm gap, interdigitated-electrode photomixer operating at room temperature and pumped by two modes of a Ti:Al2O3 laser separated in frequency by 0.2 GHz. The output power and associated optical-to-electrical conversion efficiency of 1% represent more than a sixfold increase over previous LTG-GaAs photomixer results obtained at room temperature. A separate LTG-GaAs photomixer having 0.6 μm gaps generated up to 0.1 mW at room temperature and up to 4 mW at 77 K. Low-temperature operation is beneficial because it reduces the possibility of thermal burnout and it accentuates a nearly quartic dependence of output power on bias voltage at high bias. The quartic dependence is explained by space-charge effects which result from the application of a very high electric field in the presence of recombination-limited transport. These conditions yield a photocurrent-voltage characteristic that is very similar in form to the well-known Mott–Gurney square-law current in trap-free solids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111289
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  • 5
    Electronic Resource
    Electronic Resource
    Quantum well intersubband heterodyne infrared detection up to 82 GHz (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1594-1596 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate the heterodyne detection of two CO2 laser signals offset in frequency up to 82.16 GHz using a multiple quantum well intersubband infrared photodetector. The high frequency is reached by down conversion using the detector itself as a microwave or millimeter-wave mixer. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114950
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  • 6
    Electronic Resource
    Electronic Resource
    Photomixing up to 3.8 THz in low-temperature-grown GaAs (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 285-287 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature-grown (LTG) GaAs is used as an optical-heterodyne converter or photomixer, to generate coherent continuous-wave output radiation from microwave frequencies up to 3.8 THz. The photomixer consists of an epitaxial layer of LTG GaAs with interdigitated electrodes fabricated on the top surface. Terahertz photocurrents are generated in the gaps between the electrodes, and power is radiated into free space through a three-turn self-complementary spiral antenna. In a photomixer having a 0.27-ps electron-hole lifetime and small electrode capacitance, the output power is practically flat up to about 300 GHz and then rolls off at a rate of approximately 12 dB/oct. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113519
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  • 7
    Electronic Resource
    Electronic Resource
    Measurements of optical-heterodyne conversion in low-temperature-grown GaAs (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1206-1208 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A low-temperature-grown GaAs interdigitated-electrode photomixer is used to generate coherent power at microwave frequencies. An output power of 200 μW (−7 dBm) is generated by pumping the photomixer with two 70-mW modes of a Ti:Al2O3 laser, separated in frequency by 200 MHz. This represents an optical-to-microwave conversion efficiency of 0.14%, which is within 50% of a prediction based on optical-heterodyne theory. When two lasers are used and the frequency of one is tuned with respect to the other, the output frequency of the photomixer increases smoothly and the output power is nearly constant up to 20 GHz. At higher frequencies the power decays because of parasitic capacitance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108735
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  • 8
    Electronic Resource
    Electronic Resource
    Three-dimensional metallodielectric photonic crystals exhibiting resonant infrared stop bands (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 2937-2939 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using standard microelectronic techniques, we have fabricated arrays of infrared metallodielectric photonic crystals (IR MDPCs) on silicon substrates. The metallic "atoms" are located on a three-dimensional (100)-oriented face-centered-cubic lattice. Resonant stop-band characteristics have been measured with rejection levels of up to 20 dB and widths of up to 83% of the center frequency. We demonstrate structures with stop bands across the midinfrared wavelength range from 2 to 12 μm. Angular studies of the photonic stop bands show an insensitivity to incident angle for some of the structures. The IR MDPC results are compared with measurements made on microwave-scale MDPC structures to help in understanding the infrared results. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118749
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  • 9
    Electronic Resource
    Electronic Resource
    Generation and detection of coherent terahertz waves using two photomixers (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3824-3826 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A general technique has been demonstrated at microwave and submillimeter-wave frequencies for photoconductive sampling in the frequency domain using photomixers and continuous-wave laser diodes. A microwave version in which two photomixers were coupled by a transmission line was developed to quantitatively test the concept from 0.05 to 26.5 GHz. A quasioptical version using antenna-coupled photomixers was demonstrated from 25 GHz to 2 THz. Such a system can outperform systems based on time-domain photoconductive sampling in frequency resolution, spectral brightness, system size, and cost.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122906
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  • 10
    Electronic Resource
    Electronic Resource
    Terahertz measurements of resonant planar antennas coupled to low-temperature-grown GaAs photomixers (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3632-3634 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Resonant slot and dipole antennas coupled to low-temperature-grown GaAs photomixers have been fabricated and tested at terahertz operating frequencies. Enhanced output power is seen from the resonant structures compared to mixers coupled to broadband self-complementary spiral antennas. Driving point impedances as high as 300 Ω are attained at the resonant frequencies. These devices will be useful as fixed frequency local oscillators for submillimeter heterodyne receivers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117006
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