Experimental Comparison of UTC- and PIN-Photodiodes for Continuous-Wave Terahertz Generation

Abstract

We carried out an experimental comparison study of the two most established optoelectronic emitters for continuous-wave (cw) terahertz generation: a uni-traveling-carrier photodiode (UTC-PD) and a pin-photodiode (PIN-PD). Both diodes are commercially available and feature a similar package (fiber-pigtailed housings with a hyper-hemispherical silicon lens). We measured the terahertz output as a function of optical illumination power and bias voltage from 50 GHz up to 1 THz, using a precisely calibrated terahertz power detector. We found that both emitters were comparable in their spectral power under the operating conditions specified by the manufacturers. While the PIN-PD turned out to be more robust against varying operating parameters, the UTC-PD showed no saturation of the emitted terahertz power even for 50 mW optical input power. In addition, we compared the terahertz transmission and infrared (IR) blocking ratio of four different filter materials. These filters are a prerequisite for correct measurements of the absolute terahertz power with thermal detectors.

Photodiodes for Terahertz Applications

“…An ideal current source corresponding to the measured photocurrent of 12.5 mA was used as the source current in the model. There is a maximum in the output power of 0.5 mW at 100 GHz which agrees well with the numerical simulations and is higher than the values reported in [77] for comparable optical input powers, i.e. 40 mW p-i-n photodiode in [77] vs 50 mW for the UTC-PD.…”

“…There is a maximum in the output power of 0.5 mW at 100 GHz which agrees well with the numerical simulations and is higher than the values reported in [77] for comparable optical input powers, i.e. 40 mW p-i-n photodiode in [77] vs 50 mW for the UTC-PD. This corresponds to the point in the impedance model where the UTC-PD impedance is closest to the complex conjugate of the antenna impedance as mentioned earlier.…”

“…For the unpackaged slot antenna, a responsivity of 0.25 A/W was measured with 50 mW optical input power. The responsivity is higher than the UTC-PD reported in [77] but lower than the reported p-i-n PD responsivity. The THz output power was first recorded using the calibrated TK power meter up to 300 GHz and from 150-500 GHz using the GC.…”

A Review on Terahertz Technologies Accelerated by Silicon Photonics

“…It is a common device used in current THz wireless communication systems. Of course, these technologies are still evolving rapidly, and the latest work compares the performance of two typical commercially available photomixers: UTC-PD and PIN-PD [ 47 ]. The UTC-PD emits ~100 μW at 250 GHz, and the PIN-PD produces 30 μW.…”

Beyond 110 GHz Uni-Traveling Carrier Photodiodes on an InP-Membrane-on-Silicon Platform

“…These characteristics therefore make UTC-PDs an interesting device for high speed communications, but also enable the generation of high frequency signals due to its ability to reach bandwidths >100 GHz. High bandwidth photomixers based around a UTC-PD have already demonstrated reaching frequencies up to 1 THz [11].…”