Multi-material heterogeneous integration on a 3-D Photonic-CMOS platform

Photonics has been one of the primary beneficiaries of advanced silicon manufacturing. By leveraging on mature complementary metal-oxide-semiconductor (CMOS) process nodes, unprecedented device uniformities and scalability have been achieved at low costs. However, some functionalities, such as optical memory, Pockels modulation, and magnetooptical activity, are challenging or impossible to acquire on group-IV materials alone. Heterogeneous integration promises to expand the range of capabilities within silicon photonics. Existing heterogeneous integration protocols are nonetheless not compatible with active silicon processes offered at most photonic foundries. In this work, we propose a novel heterogeneous integration platform that will enable wafer-scale, multi-material integration with active silicon-based photonics, requiring zero-change to existing foundry process. Furthermore, the platform will also pave the way to a class of high-performance devices. We propose a grating coupler design with peak coupling efficiency reaching 93%, an antenna with peak diffraction efficiency in excess of 97%, and a broadband adiabatic polarization rotator with conversion efficiency exceeding 99%

High-speed 4 ×{\times} 4 silicon photonic electro-optic switch, operating at the 2 {\mu}m waveband

The escalating need for expansive data bandwidth, and the resulting capacity constraints of the single mode fiber (SMF) have positioned the 2-${\mu}$m waveband as a prospective window for emerging applications in optical communication. This has initiated an ecosystem of silicon photonic components in the region driven by CMOS compatibility, low cost, high efficiency and potential for large-scale integration. In this study, we demonstrate a plasma dispersive, 4 ${\times}$ 4 electro-optic switch operating at the 2-${\mu}$m waveband with the shortest switching times. The demonstrated switch operates across a 45-nm bandwidth, with 10-90% rise and 90-10% fall time of 1.78 ns and 3.02 ns respectively. In a 4 ${\times}$ 4 implementation, crosstalk below -15 dB and power consumption below 19.15 mW across all 16 ports are indicated. The result brings high-speed optical switching to the portfolio of devices at the promising waveband

Crown ether decorated silicon photonics for safeguarding against lead poisoning

Lead (Pb2+) toxification in society is one of the most concerning public health crisis that remains unaddressed. The exposure to Pb2+ poisoning leads to a multitude of enduring health issues, even at the part-per-billion scale (ppb). Yet, public action dwarfs its impact. Pb2+ poisoning is estimated to account for 1 million deaths per year globally, which is in addition to its chronic impact on children. With their ring-shaped cavities, crown ethers are uniquely capable of selectively binding to specific ions. In this work, for the first time, the synergistic integration of highly-scalable silicon photonics, with crown ether amine conjugation via Fischer esterification in an environmentally-friendly fashion is demonstrated. This realises a photonic platform that enables the in-situ, highly-selective and quantitative detection of various ions. The development dispels the existing notion that Fischer esterification is restricted to organic compounds, laying the ground for subsequent amine conjugation for various crown ethers. In this work, the platform is engineered for Pb2+ detection, demonstrating a large dynamic detection range of 1 - 262000 ppb with high selectivity against a wide range of relevant ions. These results indicate the potential for the pervasive implementation of the technology to safeguard against ubiquitous lead poisoning in our society

Development of hybrid/active/passive silicon photonics for future technologies

As a corollary of silicon manufacturing, silicon photonics has emerged as a viable photonic platform that has attracted the attention of many. The commercialization efforts of this technology, however, have remain somewhat limited due to several obstacles, technical and cost-related. As silicon is a poor emitter of light, the realization of an electrically-pumped monolithic laser source is unlikely. However, one may argue that the above have been satisfactorily resolved with the hybrid/heterogenous Ⅲ-Ⅴ/silicon photonic platform. In fact, the poor electro-optic conversion of silicon is one of the main factor that enables high performance hybrid/heterogenous Ⅲ-Ⅴ/silicon photonic laser diodes, resulting in significant improvement in performance over its Ⅲ-Ⅴ counterparts. While silicon photonics promises low cost, the premise is that the economies of silicon manufacturing is exploited. The inception of silicon photonics is mainly driven by the “interconnect bottleneck” in telecom and datacom. The data center transceiver market is attractive. However, there is a lack of a singular solution to all requirements in terms of reach, multisource agreement and standards. This implies that the cost of developing silicon photonics technology will be high unless the optical industry makes a concerted effort for standardization. As of now, the volumes required by silicon photonics are too low to draw commitment from large chip-making foundries. This work posits that for silicon photonics to be commercially viable, its range of applications must be widespread. The greater the adoption of silicon photonics in industry, the lower its cost. The condition is that firms must make the first step towards choosing silicon photonics for their applications. This work focuses on the development of silicon photonics technology beyond the traditional O and C bands. As a proof of concept to the broadband properties of the silicon-on-insulator platform, a high-performance arbitrary power splitter is realized at the longer transparency edge. In regard to the 2 μm waveband, which has been touted as a potential window for optical communications, the active Si-SiN multilayer platform, silicon switching as well as hybrid Ⅲ- Ⅴ/silicon photonic tunable lasers operating from 1881-1947, 1955-1992 nm has been demonstrated for the first time. In addition, at the application-rich wavelength region near 1.65 µm, a sub-kHz linewidth, hybrid Ⅲ-Ⅴ/silicon photonic tunable laser with a range of 1647-1690 nm is reported.Doctor of Philosoph

Optical frequency comb generation from a 1.65 µm single-section quantum well laser

Optical frequency combs (OFCs) in the 1.65 µm wavelength band are promising for methane sensing and extended high-capacity optical communications. In this work, a frequency-modulated (FM) OFC is generated from a 1.65 µm single-section quantum well laser. This is characterized by a 1 kHz-wide beatnote signal at ∼19.4 GHz. Typical FM optical spectra are shown and optical linewidth of the OFC narrows through the mutual injection locking process in the comb formation. No distinct pulse train is observed on oscilloscope, which conforms with the FM operation. Furthermore, to add further evidence that four-wave mixing (FWM) is the driving mechanism of the comb formation, FWM frequency conversion characterization is conducted on a semiconductor optical amplifier (SOA) fabricated together with the tested laser. An efficiency of ∼-30 dB confirms the capability of FM mode locking.National Research Foundation (NRF)Published versionNational Research Foundation Singapore (NRF-CRP12-2013-04); Finance Science and Technology Project of Hainan Province (ZDYF2020036); National Natural Science Foundation of China (61964007)

Temperature-dependent phase noise properties of a two-section GaSb-based mode-locked laser emitting at 2 μm

The temperature-dependent phase noise properties of a monolithic two-section mode-locked semiconductor laser are first investigated. This is performed on a GaSb-based quantum well laser emitting at ∼2 μm. Stable mode locking operation with a fundamental repetition frequency of ∼13.3 GHz is achieved on this laser up to 60 °C. At a fixed temperature, there is no monotonous dependence of integrated jitter on the bias condition. For a given gain current or absorber voltage, there exists a corresponding optimal absorber voltage or gain current, respectively, that minimizes the integrated jitter. More important, the phase noise properties improve obviously at elevated temperatures with the lowest achievable jitter reducing obviously from 3.15 ps at 20 °C to 1.39 ps at 60 °C (100 kHz–1 GHz). We consider that the reason is reduced amplified spontaneous emission noise at high temperatures. This is confirmed by the extracted peak-to-valley ratio of the involved laser modes. We believe that this study provides an important insight into the carrier behaviors and noise performance of mode-locked semiconductor lasers, which is meaningful to their applications especially at high temperatures.National Research Foundation (NRF)Published versionThis work was supported in part by the National Research Foundation of Singapore (No. NRF-CRP12-2013-04), the National Natural Science Foundation of China (Nos. 61964007 and 61790582), and the Key-Area Research and Development Program of Guangdong Province (No. 2020B0303020001)

Analysis of compact Silicon Photonic Hybrid Ring External Cavity (SHREC) wavelength-tunable laser diodes operating from 1881-1947 nm

The “2 μm waveband”, specifically the 1.9 μm wavelength region, is playing an increasingly imperative role in photonics. Development into compact tunable light sources operating at the wavelength region can unlock numerous technological applications. Instances, while not exhaustive, include alleviating the capacity load in fiber communications, H2O spectroscopy, optical logic, signal processing as well as enabling the optical Kerr effect on silicon. Silicon photonics is a disruptive technology. Through mature silicon processing, recent developments suggest that silicon will emerge as the workhorse of integrated optics. While the realization of a monolithic light source has proved to be challenging, the hybrid/heterogenous Si platforms, consisting of silicon and III-V materials, has stepped to the fore. In this work, we present the study of Vernier-based hybrid silicon photonic wavelength-tunable lasers with an operating range of 1881-1947 nm (66 nm), subject to different coupling gaps ...&mor

1 × <i>N</i> (<i>N</i> = 2, 8) Silicon selector switch for prospective technologies at the 2 μm waveband

The 2 µm waveband, specifically near 1.9 µm, is an imperative resource that could possibly be exploited in future communications systems. This is due to the promising infrastructural developments at the wavelength region (hollow-core photonic bandgap fiber, thulium-doped fiber amplifier) near 1.9 µm. In this work, we report the 1 × N selector switch based on Mach-Zehnder interferometers operating near the 1.9 µm wavelength region. As an elementary cell (N = 2), an insertion loss as low as 1.1 dB, Pπ of 23 mW, 10-90 % switching time of lower than 38 µs and a crosstalk of lower than -25 dB from 1880 to 1955 nm has been determined. In order to prove scalability, the 1 × 8 switch (N = 8) is demonstrated, indicating crosstalk as low as -21 dB, considering all possible switching configurations across the abovementioned wavelength region. Insertion loss levels are examined

Sub-kHz linewidth, hybrid III-V/silicon wavelength-tunable laser diode operating at the application-rich 1647-1690 nm

The wavelength region about of 1650 nm enables pervasive applications. Some instances include methane spectroscopy, free-space/fiber communications, LIDAR, gas sensing (i.e. C2H2, C2H4, C3H8), surgery and medical diagnostics. In this work, through the hybrid integration between an III-V optical amplifier and an extended, low-loss wavelength tunable silicon Vernier cavity, we report for the first time, a III-V/silicon hybrid wavelength-tunable laser covering the application-rich wavelength region of 1647-1690 nm. Room-temperature continuous wave operation is achieved with an output power of up to 31.1 mW, corresponding to a maximum side-mode suppression ratio of 46.01 dB. The laser is ultra-coherent, with an estimated linewidth of 0.7 kHz, characterized by integrating a 35 km-long recirculating fiber loop into the delayed self-heterodyne interferometer setup. The laser linewidth is amongst the lowest in hybrid/heterogeneous III-V/silicon lasers.</p

Mid-infrared (MIR) Mach-Zehnder silicon modulator at 2μm wavelength based on interleaved PN junction

In this paper, a MIR silicon modulator operating at 2 μm wavelength is experimentally demonstrated. The modulator shows 9.7 GHz 3-dB electro-optic bandwidth at Vbias= -3V. We also present optical modulation at 12.5 Gb/s.</p