Active photonic integrated circuits using semiconductor optical amplifiers Yiwei Xie, Leimeng Zhuang, Arthur James Lowery Electro-Photonics Laboratory, Dept. of Elec. and Computer Sys. Eng., Monash University, Wellington Road, Clayton, Australia yiwei.xie@monash.edu; leimeng.zhuang@monash.edu; arthur.lowery@monash.edu Abstract— Active photonic circuits use combinations of active semiconductor devices and passive elements to support many applications. We present four functions on a single active photonic integrated circuit (4.5 mm × 4 mm). Keywords-Integrated photonic circuits; ring resonator; semiconductor optical amplifier I. INTRODUCTION Photonic signal processing, using photonic approaches to condition optical signals, offers advantages of large time- bandwidth capabilities to overcome inherent electronic speed limitations, and immunity to electromagnetic interference (EMI) [1]. Active Photonic Circuits [2] combine active semiconductor devices and passive elements to provide novel functionality, such as high-speed demultiplexing, microwave photonics [3], optical packet switching and optical instrumentation [4]. The active element is usually a semi-conductor optical amplifier (SOA), as SOAs have advantages of high optical gain per unit length, and can be switched using their injection current. To date, most of the applications using SOAs have been realized by discrete optical components, having their optical paths connected using optical fibers [3-4]. In this paper, we present a new photonic integrated circuit (PIC) design using indium phosphide (InP) technology, in which the key optical element is a SOA. We have demonstrated the PIC’s functions include: delay discriminator, optical sampler, tunable delay line, and wavelength converter. II. OVERVIEW OF THE PIC Lowery [2] analyzed and simulated many photonic integrated circuits based on SOAs in 2005, four applications are shown in Fig. 1a. We have designed and developed these topologies onto a PIC, which has been fabricated via the JePPIX foundry service using SMART Photonics’ InP platform (Fig. 1b). This has shallow-etched InP waveguides with a propagation loss of 3.5 dB/cm and coupling loss of about 4 dB from a facet to a lensed fiber. We have used the structures on the PIC, and demonstrated four separate functions, described in the next section. III. APPLICATIONS OF THE PIC We have characterized various parts of the chip and shown their utility in several applications, described below. A. Delay discriminator The comparison of the arrival times of modulated optical waveforms is critical to the design of all-optical clocks using phase-locked loops. The delay discriminator was first proposed by Lowery and Premaratne in 2005 [5], we have developed and demonstrated this device in [6]. Part 2 in Fig. 1c shows the structure of the device, which contains a serial cascade of three sections of SOAs and two integrated photodiodes (PD). Forward and backward propagating pulse are injected into a cascade of three sections of SOAs from opposite sides. The left- and right-facet output signals of the SOA are individually detected by PDs. If a forward- propagating pulse leads a backward-propagating pulse, then This work is funded by Australian Research Council Laureate Fellowship FL 130100041. Figure 1: (a) Common topologies of active photonic circuits [2]. Arrows indicate the signal directions. (b) A photomicrograph of our PIC. (c) Mask layout. Parts (1), (3) Delay discriminator with forward-and reverse signal monitoring; (2) Delay discriminator with outwards-signal monitoring; (4) SOA with 1s2 couplers; (5) SOA in ring resonator; (6) MZI with SOAs for wavelength conversion; (7),(8) Sagnac Loop with SOA.