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An active-passive integration technique for operation near a wavelength of 1030 nm has been developed on a gallium arsenide (GaAs) photonic integrated circuit platform. The technique leverages quantum wells (QWs) that are slightly offset vertically from the center of the waveguide, and selectively removed prior to upper cladding regrowth to form active and passive regions. The active region consists of indium gallium arsenide (InGaAs) QWs, gallium arsenide phosphide (GaAsP) barriers, GaAs separate confinement heterostructure layers, and aluminum gallium arsenide (AlGaAs) cladding. Fabry Perot lasers with various widths were fabricated and characterized, exhibiting high injection efficiency of 98.8%, internal active loss of 3.44 cm−1, and internal passive loss of 4.05 cm−1 for 3 μm wide waveguides. The 3 μm, 4 μm, and 5 μm wide lasers demonstrated greater than 50 mW output power at 100 mA continuous wave (CW) current and threshold current as low as 9 mA. 20 μm wide broad area lasers demonstrated 240 mW output power, 35.2 mA threshold current under CW operation, and low threshold current density of 94 A/cm2 for 2 mm long lasers. Additionally, these devices exhibit transparency current density of 85 A/cm2 and good thermal characteristics with T 0 = 205 K, and Tη = 577K.

An indium phosphide photonic integrated circuit (PIC) was demonstrated for integrated path differential absorption lidar of atmospheric carbon dioxide (CO2). The PIC consists of two widely tunable sampled grating distributed Bragg reflector (SGDBR) lasers, directional couplers, a phase modulator, a photodiode, and semiconductor optical amplifiers (SOAs). One SGDBR laser, the leader, is locked to the center of an absorption line at 1572.335 nm using the on-chip phase modulator and a bench-top CO2 Herriott reference cell. The other SGDBR laser, the follower, is stepped in frequency over ±15 GHz around 1572.335 nm to scan the target CO2 absorption line. The follower laser is offset locked to the leader laser with an optical phase lock loop. An SOA after the follower laser generates a pulse at each frequency step to create a train of pulses that samples the target CO2 absorption line. The PIC components and subsystem are characterized and evaluated based on target performance requirements. The leader laser demonstrated a 236-fold improvement in frequency stability standard deviation when locked compared to free running and the follower laser frequency stability standard deviation compared to the leader laser was 37.6 KHz at a 2 GHz programmed offset.

We present recent progress on a photonic integrated lidar system for carbon dioxide (CO 2 ) active remote sensing at 1572.335 nm. With integration, the cost, size, weight and power (CSWaP) of the system are significantly improved. System and subsystem level results are demonstrated.

Indium phosphide (InP) is the most developed platform for photonic integrated circuits (PICs). Of interest is the advancement of this platform for applications that demand high performance, especially high output power, including free space communications and microwave photonics. In this paper, we summarize development of InP-based PIC transmitters. Two transmitter types were fabricated: one based on an offset quantum wells (OQW) platform and the other on a quantum well intermixing (QWI) platform. The OQW-based transmitter consists of a widely tunable laser, a high-speed semiconductor optical amplifier (SOA), a Mach–Zehnder modulator, and an output SOA. This transmitter demonstrates a 44-nm tuning range, >45 dB side mode suppression ratio, 14.5 dBm off -chip power, and a data rate of 7 Gbps. The second transmitter, based on QWI, utilizes an alternate epitaxial structure to achieve a lower confinement factor for higher SOA output saturation power. This QWI transmitter consists of a distributed Bragg reflector laser, a high-speed SOA, an electroabsorption modulator, and an output SOA. The measured off -chip power is 19.5 dBm, and a data rate of 20 Gbps is demonstrated. Based on the improved performance with the new epitaxial structure, a novel platform for high-power PIC transmitters integrated with low confinement and high-power SOAs is described.

Subsystem operation of a photonic integrated circuit for low size, weight, and power remote gas sensing was demonstrated. Precision lidar system specifications for laser tuning, photodiode bandwidth and pulse extinction ratio were satisfied. A twentyfold improvement in long-term laser frequency stability was achieved.

A novel indium phosphide Mach-Zehnder interferometer with directional couplers was realized to compensate residual amplitude modulation in integrated phase modulators. The change in transmission for π phase shift was reduced from 3.85 dB to 1.98 dB.

A dual laser indium phosphide photonic integrated circuit for remote sensing lidar was realized. A twentyfold improvement in the long-term frequency stability of the master laser was demonstrated using an on-chip phase modulator.

An active-passive integration platform on GaAs is demonstrated with Fabry Perot lasers exhibiting up to 240 mW total output power, 98.8% injection efficiency, and 3.44 cm-1 active loss for operation near 1030 nm.

We present the design strategy of shallow-angle grating couplers for vertical emission from InP devices, and then discuss the focusing effect of a 2D grating. Measured beam shapes from prototyped devices agree well with the simulation results.

MOCVD grown aluminum-free quantum dot lasers have been demonstrated with a maximum wall-plug efficiency of 30%, a lowest threshold current of 8 mA, and a maximum single-facet output power of 200 mW.

Publisher’s Note: This paper, originally published on 6 September 2019, was replaced with a corrected version on 10 October 2019. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance.

In this work, a high-power indium phosphide photonic integrated circuit was investigated for pulse position modulation free space optical communications. The integrated transmitter was fabricated with a novel high-power platform. 16-ary pulse position modulation was demonstrated at a data rate of 1.25 Gbps with an extinction ratio of 9.6 dB.

We report on a monolithic indium phosphide photonic integrated transmitter capable of generating high-speed return-tozero differential phase shift keying (RZ-DPSK) data streams for space optical communications as high as 5 Gbps. The integrated transmitter includes a sampled grating distributed Bragg reflector laser continuously tunable over 30 nm in the C-band, a semiconductor optical amplifier for amplification, a Mach-Zehnder modulator for encoding phase-shift-keying data, and electro-absorption modulator for return-to-zero pulse carving. The transmitter is situated in a custom electronics test bed for biasing various PIC sections and driving the modulators. Furthermore, this transmitter can also be utilized for 10 Gbps DPSK or NRZ-OOK.

We present recent progress on a wavelength tunable, pulsed laser source for laser spectroscopy of CO 2 at 1572 nm. An integrated photonics design in indium phosphide (InP) is presented and compared to a fiber-component-based implementation. Significant improvement in size, weight and complexity is demonstrated.

High-power photonic integrated circuits (PICs) are of interest for a variety of applications including microwave photonics, free space optical communications and coherent LiDAR systems [1], [2]. Indium phosphide (InP) is the most advanced platform for high-performance PICs. InP PICs are particularly attractive for free space optical communications, which requires low cost, size, weight and power (CSWaP) [3]–[5]. In conventional InP PICs, saturation power of semiconductor optical amplifiers (SOAs) is limited by small modal size and high confinement factor ( $> 5\%$ ). To improve the SOA saturation power, one approach is to increase the modal size with a flared waveguide, but the large beam dimension in the horizontal direction imposes challenges on the coupling to singlemode fiber [6]. A second approach is to reduce the confinement factor. Slab-coupled optical waveguides (SCOW) with small confinement factor have been investigated for high-power SOAs and lasers. However, it is very challenging to monolithically integrate the SCOW SOAs with other optical elements required for a PIC such as a seed laser and modulator [7]. In this work, we have proposed a novel platform enabling the monolithic integration of low-confinement SOAs with other high-confinement components including a distributed Bragg reflector (DBR) laser and high-speed electro-absorption modulator (EAM).

We present results of an indium phosphide (InP) monolithic photonic integrated circuit (PIC) transmitter suitable for space-optical communications up to 10 Gbps for NRZ-OOK and DPSK modulation and up to 5 Gbps RZ-DPSK modulation. The PIC includes an SG-DBR laser tunable across the entire telecommunications C-Band, a semi-conductor optical amplifier (SOA), a Mach-Zehnder modulator (MZM) for efficient encoding of phase information, and an electroabsorption modulator (EAM) which serves as an RZ pulse carver. The transmitter PIC is integrated in a testbed with a custom board that provides biasing and driving electronics. The commercial-off-the-shelf (COTS) differential driver generates an estimated 4.5-5 Vpp differential modulation voltage for the dual drive MZM. An identical driver was used for the EAM 50% RZ pulse carver but only a single output was used with the other output terminated with a 50Ω load. The SOA and laser gain sections were biased at 90 mA each. Clear eye openings were achieved for all modulation formats.

A summary of photonic integrated circuit (PIC) platforms is provided with emphasis on indium phosphide (InP). Examples of InP PICs were fabricated and characterized for free space laser communications, Lidar, and microwave photonics. A novel high-performance hybrid integration technique for merging InP devices with silicon photonics is also discussed.

Integrated laser transmitters are demonstrated for free space communications. The sampled grating DBR laser is tunable from 1521 nm to 1565 nm while maintaining >45 dB side mode suppression ratio. The transmitters demonstrate a 3-dB linewidth of 6.4 MHz and 7 Gbps data rate.

Two approaches to ripple free 1 × 4 optical beamforming networks are presented; one is based on a 5-stage Mach-Zehnder switchable delay line and the other on a 3-optical-ring-resonator delay line. Both are demonstrated for W-band communications.

An optical ring resonator (ORR) based 1 × 4 integrated optical beamforming network (OBFN) targeting mmW is reported. The optimized true time delay response of a 3-ORR delay line with a bandwidth of 8.7 GHz was achieved over tuning range of 172.4 ps, which corresponds to a 31π phase shift for a 90 GHz signal. A 3 Gbps OOK NRZ data signal was transmitted through the delay line to verify the overall performance. A 49° beamsteering angle equivalent OBFN delay response was achieved for a 90 GHz half-wavelength dipole antenna array. Using heterodyne upconversion technology and a single delay path, 41 GHz mmW signal with 3 Gbps OOK NRZ data modulation was generated and delayed.

The delay response and sharing topology of a 3-optical-ring-resonator based optical beamforming network were experimentally studied and optimized. Eye diagrams were measured to evaluate the signal degradation imposed by the chip.