Packaging High Power Photodetectors for 100 MHz to 100 GHz RF Photonic Applications

ABSTRACT: In this SBIR effort we will develop a packaging process and demonstrate (Phase I) a prototype of high power Photodiode (PD) that has a normal incident, pigtailed fiber input and a coaxial RF output that operates from DC to>60GHz. We will apply and extend (Phase II) the aforementioned packaging process to single PD, balanced PD and array of PDs that work from DC through entire W-band. Demand of such packaging methods and processes arose from recent progress in PDs and array of PDs based on modified uni-traveling-carrier (MUTC) thin-layered structures. The speed, bandwidth, and high power of these devices generate great interests of direct RF generation in microwave photonic system for simplification, higher gain, wider dynamic range and lower Noise Figure (NF). However, performance, especially saturation photocurrent of these PDs is critically affected by the packaging material, structure and process. Therefore, developing a reliable, efficient, cost-effective and adaptable packaging approach lies on the critical path toward optical down-conversion and direct RF generation in modern microwave photonic system. Leveraging the experiences of fabricating and packaging ultra-broadband optical and millimeter-wave components, PSI has the knowledge base and unique capabilities of accomplishing this goal. BENEFIT: The potential applications for high-frequency, high-power photodiode technology and its capabilities are vast and could have a profound impact on our society. Traditionally, photodiode is made for detection of photonic input signal based on EO effects. Today, as high frequency microwave, millimeter wave and terahertz range are rapidly explored, photodiodes, especially ones with high output power, have become critical devices and indispensable ways of photonic link demodulation or high frequency signal generation. For example, Terahertz or sub-Terahertz frequencies have proven to be a powerful tool for spectroscopic measurement of far-infrared material properties for dielectrics, semiconductors, liquids and gases, etc., since most chemical compounds show very strong frequency-dependent absorption and dispersion in this frequency range. However, generation of such high frequency signal with enough power is very challenging for practical applications. Among all the solutions, optical based methods that rely on high-frequency and high-power PDs are greatly favored due to its wide bandwidth and configurability. The similar reasons, along with potential high available output power, PDs are vastly investigated and applied for Radio-on-fiber broadband wireless communications, which is propelled by the huge increase of data volume in recent years. According to Edholm"s law, the demand for point-to-point bandwidth in wireless short-range communications has doubled every 18 months over the last 25 years. It can be predicted that data rates of around 510 Gb/s will be required in ten years. Tremendous market demands of high power PDs are expected by then. A list of potential applications of high-frequency, high-power PD includes: a) Spectroscopic applications including imaging, tomography, cancer detection or genetic analysis. b) Material identification such as detection of explosives and related compounds for defense and security applications. c) Broadband short distance wireless communications. d) Broadband phased antenna arrays, radar systems and warfare systems. e) Microwave photonic link system for all-optical backbone microwave distribution. More specifically, PSI will seek and identify applications of high-frequency and high-power PDs in broadband phase array antennas and microwave photonic link system as a platform for multifunctional radar systems, where hundreds or thousands of PDs are required in a single system. To this end, packaged PD module with small size, light weight, low cost and easy-to-deploy interface not only represents an impressive leap forward in our technical capabilities but also a tremendous business opportunity. & #8195;