|
|
|
|
|
|
|
Shubhashish Datta & Abhay M. Joshi*
Discovery Semiconductors Inc., Ewing, NJ, USA
ABSTRACT
We present uncooled, fiber-coupled InGaAs photodiode modules for DC to 18 GHz applications that generate broadband linear RF signal with peak-to-peak output amplitude up to 4 Vpp and phase nonlinearity, i.e. power-to-phase conversion factor < 6 rad/W. The photodiode’s phase nonlinearity approaches zero for selected operating conditions, as needed for generating precision clocks. The photodiodes demonstrate reliable operation up to a DC photocurrent of 50 mA at 9 V reverse bias at ambient room temperature of 20 °C with passive heat sinking. The photodiodes are packaged in miniature, fiber-pigtailed modules having a size, weight, and power (SWaP) that is suitable for phased array systems.
INTRODUCTION
High power, highly linear photodiodes are desirable for photonically remoted radar systems for two reasons: faithfully transferring optical signals into RF domain with low noise figure and minimal nonlinear distortions, and generating low phase noise microwave clocks to improve the dynamic range during the analog to digital conversion. Precision of clock transfer is especially important for phase array systems as timing inaccuracy impacts the reconstruction of the signals from multiple antennas and may limit the combined aperture size.
Our prior work reported thermo-electrically cooled, fiber coupled photodiode modules that demonstrate linear behavior up to an RF output of 4 Vpp, i.e. +16 dBm, at reverse bias of 12 V for X-band applications [1]. These devices have enabled challenging analog applications, including 12 GHz carrier generation with <-170 dBc/Hz phase noise [2]. In this work, we report uncooled, fiber-coupled photodiode modules having similar power handling and linearity at a reduced photodiode reverse bias of 9 V. Elimination of the thermo-electric cooler inside the photodiode module not only reduces the power consumption of the module by 2 to 3 W, but also leads to 7-fold reduction in the size of the package, which enables a two-dimensional array having a pitch as small as 8 mm.
REFERENCES
- [1] S. Datta and A. Joshi, “High-Power Highly Linear Photodiodes for High Dynamic Range LADARs,” in 18th Coherent Laser Radar Conf. CLRC 2016, 27 June – 1 July 2016, Boulder, Colorado, USA.
- [2] X. Xie, R. Bouchand, D. Nicolodi, M. Giunta, W. Hansel, M. Lezius, A. Joshi, S. Datta, C. Alexandre, M. Lours, P. Tremblin, G. Santarelli, R. Holzwarth, and Y. Le Coq, “Photonic microwave signals with zeptosecond-level absolute timing noise,” Nature Photonics, vol. 11, pp. 44 – 48, 2017.
Event: SPIE Defense + Commercial Sensing, 2021, Online Only
