Optical and terahertz power limits in the low-temperature-grown GaAs photomixers

Abstract

High-order harmonic generation at 4MHz as a light source for time-of-flight photoemission spectroscopy

Broadband Terahertz Source Based on Photomixing in Laser-Assisted Field Emission with Clusters of Carbon Nanotubes

“…The total mixer current in the load would be 1.06 mA peak, for an output power of 28 μW. This is 14 dB greater than that from photomixing in LTG GaAs (Verghese et al, 1997) For the special case where the characteristic impedance and phase delay of each transmission line are equal to Z 0 and , respectively, and the mixer current is the same in each line, the power that is delivered to the load is multiplied by what it would be for a single field emitter, where the multiplying factor is given by …”

“…Again, the radiation resistance and reactance of the antenna would constitute the load impedance. A variety of different types of antennas have been used at THz frequencies including dipole and bow tie (Yano et al, 2005), spiral (Verghese et al, 1997), and log-periodic structures (Mendis et al, 2005). We have also studied the zigzag antenna for broadband applications of LAFE at THz frequencies (Alonso et al, 2001).…”

“…However, the present sources of THz radiation present "hurdles" because of their limited tunable bandwidth and output power, and some require fragile, large, and expensive femtosecond lasers or even particle accelerators (Zhang, 2002). Some of the methods that have been used to generate THz radiation are backward wave oscillators with chains of frequency multipliers (Maiwald et al, 2000), the Smith-Purcell Effect (Mross et al, 2003), quantum cascade lasers (Davies et al, 2002), synchrotron radiation from high-energy accelerators (Carr et al, 2002), bulk electro-optic rectification and ultrafast charge transport in semiconductors (Davies et al, 2002), and photomixing in semiconductors (Verghese et al, 1997). For example, photomixing (optical heterodyning) of two lasers at different wavelengths in low-temperature-grown (LTG) GaAs at the feed point of an antenna can generate an output power of only 1 µW at 1 THz, which falls off by 12 dB per octave or 1/F 4 at higher frequencies (F), so the power is reduced to 100 pW at 10 THz.…”

Tunable, continuous-wave Terahertz photomixer sources and applications

“…97 In that paper, a maximum dissipated power of approximately 45 mW was calculated for a mesa cross section of 79 lm 2 and mesa height of 1 lm, assuming a maximum heating to 120 C as specified by Brown et al for LT-GaAs. 65 This example indicates that thick InGaAs layers in a device structure may lead to serious problems with heating even at moderate laser powers. These values, however, may be overestimated as all the heat was assumed to be transported along the mesa into the substrate.…”

“…(47), when the device is operated at its maximum thermal load. Verghese et al 65 determined the maximum temperature rise for low temperature grown (LT) GaAs against its thermal bath to be about 120 K (measured at 77 K and 290 K bath temperature for s rec % 0:2 À 0:3 ps.) before thermal breakdown occurs.…”