Packaging of Silicon Photonics Modules and VLINK’s Micro-Connectivity on Silicon Photonics

VLINK Optics Corporation

http://vlinkoptics.com/

1. Technology Overview

Silicon-based semiconductors are the cornerstone of the modern microelectronics industry, but their development is approaching the limit. Optoelectronic technology is in the stage of rapid development. Today's semiconductor light-emitting devices are mostly made of compound materials and are not compatible with silicon microelectronics. Therefore, the integration of photonic technology and microelectronics technology is of great significance in the development of silicon-based optoelectronics science and technology. In recent years, research on silicon-based optoelectronics has made remarkable breakthroughs at home and abroad, and all developed countries in the world have made silicon-based photoelectrons a long-term development goal.Silicon-based optoelectronics include three main aspects of silicon-based photonic materials, silicon-based photonic devices, and silicon-based photonics integration. Introduced as follows:

2. Silicon-Based Photonic Materials

2.1 Silicon-based luminescent nanomaterials

The current research focuses on how to effectively control the size and density of silicon nanocrystals to form ordered nanostructures with small size and high density. The preparation method comprises self-organizing growth by independently controlling nucleation sites and nucleation processes on the solid surface, nanostructure growth on the masking pattern substrate; surface nanomachining of scanning probe microscopy, holographic lithography Nanopatterning and formation of ordered nanocrystal arrays by laser localized crystallization.

2.2 Silicon-based photonic crystal

Photonic crystals have a synthetic microstructure, a periodically varying refractive index, and a photonic band gap similar to the potential electron band gap of the semiconductor. According to the spatial distribution of the energy gap, it can be divided into one-dimensional, two-dimensional and three-dimensional photonic crystals. The practical application of photonic crystals is the focus of attention, and the combination with mature silicon technology is being in optimistic about its development. And all-silicon-based optoelectronic devices and all-silicon-based photonic devices can be produced. Therefore, preparation of silicon-based photonic crystals and their applications will be the focus of future research. Holographic ithography is the one of photonic crystal preparation methods, it has many advantages in using multi-beam interference;a large-volume periodic structure can be produced by the irradiation process, and the structure can be freely controlled multiple times. Different structures are made by controlling the light intensity, polarization direction, and phase delay.

3. Silicon-based photonic devices

3.1 Silicon-Based Light-Emitting Diode

As a light source in silicon-based optoelectronic integration, the come true of silicon-based light-emitting diodes (Si-LEDs) is a major direction in silicon-based optoelectronics research. The current research focuses on how to use suitable materials at active area to achieve high efficiency and high stability of light; from the practical point of view of the device, how to achieve Si-LED electroluminescence at room temperature. Researchers have tried three silicon-based nanomaterials for the fabrication of high-efficiency Si-LEDs, which are silicon nano quantum dots, high-purity monocrystalline silicon and Er3+ doped silicon nanocrystals. The best result reported so far is that electroluminescent LEDs made by Korean scientists based on silicon nano-quantum dots embedded in the SiNx film layer have an external quantum efficiency of up to 1.6% at room temperature.

3.2 Silicon-Based Laser

At present, three kinds of gain dielectric materials capable of generating optical gain or stimulated radiation have been initially proposed, which are ordered silicon nanocrystals with high density and small size, silicon/germanium quantum cascade structures based on internal subband transitions and A silicon-on-insulator (SOI) optical waveguide structure having stimulated Raman scattering characteristics. In the February 17, 2005 issue of Nature, Intel Corporation used the Raman effect to develop the world's first continuous light laser with silicon.

3.3 Silicon-based photodetectors

The silicon-based photodetector is an optical signal receiving device in silicon-based optoelectronic integration, which should have good optical response characteristics, high detection sensitivity, small dark current and wide frequency band. The Ge-PIN photodetectors developed by the Department of Materials Science and Engineering of the Massachusetts Institute of Technology, and it has responsivity of 600 mA/W, 520 mA/W and 100 mA/W at 1310nm, 1550 nm and 1620 nm respectively. The detector covers the entire C-band and most of the L-band range of optical communications with a 3dB bandwidth of 2.5GHz, and its performance at 1310nm and 1550nm is comparable to commercial InGaAs detectors which is currently used for communications.

3.4 Silicon-based light modulator

A light modulator is an optical waveguide device that modulates the phase and wavelength of transmitted light by utilizing a change in the refractive index of the material. Since silicon materials do not have a linear photoelectric effect, generally silicon-based light modulators and optical switches are designed based on the thermo-optic effect and plasma dispersion effect of silicon. In February 2004, Intel was the first to announce the successful development of Gbit/s silicon light modulators in the highly-respected Nature Science

magazine. After only one year, Intel researchers confirmed that their optical modulators have reached a transfer rate of 10 Gbit/s.

4. Silicon-based photonics integration

Although silicon optoelectronic integrated chips have not yet been developed, researchers have proposed two integrated solutions for reference: opto-electronic hybrid integration and single-chip integration. However, the silicon-based photonic integration process has great difficulty. This is because the structure of the photonic device and the electronic device is complicated, and there is a problem that the two parts are compatible with each other in the structural design. The production process is complicated, so there are problems of compatibility between various processes and front and rear processes; electrical interconnection, optical interconnection and optical coupling. The compatibility of structural design and fabrication processes is the key to enabling silicon-based photonic integration.

5. Main Research Institutions and Their Progress

5.1 University of Columbia, Optical Nanostructures Laboratory

The Optical Nanostructures Laboratory of Columbia University is currently conducting high-density, high-performance optoelectronic integrated circuit experiments through cooperation with industry partners. The goal is to use the mature CMOS technology to implement multiple optoelectronic functions on the same silicon. Their goal is to design, fabricate, and test core photonic components with minimal optical loss and perform bandwidth and nanophotonic device testing. This high performance optoelectronic integrated circuit will have a specific purpose.At Columbia University, the Silicon Photonics Research Group conducts design, numerical simulation, manufacturing and performance analysis of photonics integration on the SOI platform. The group's goal is to demonstrate the active and passive optical properties on silicon-based platforms such as light generation, control, propagation and detection. They are working on waveguide devices with a cross-sectional area of less than 0.1 square mm. This ultra-small cross section will have the following advantages: (1) a small cross section can increase the nonlinear response of the medium, so that a low power laser can be used; (2) the device can reduce the lifetime of photogenerated carriers, thus the absorption of free carriers will be greatly reduced; (3) small cross sections increase the probability of propagation. The research team at the nanoscale waveguide fabrication team will work with Dr. Vlasov and Dr. McNab from IBM's T.J. Watson Research Center. The research direction of the group includes Raman amplifier, C-band wavelength converter, magneto-optical one-way mobile isolator, fast low-power thermo-optic switch, and pulse modulation stimulated Raman scattering theory.

5.2 Institute for Microstructural Sciences National Research Council of Canada(NRC)

Taking the advantages of physical and biological sciences, NRC-IMS (National Institute of Microstructure Science, Canada) is a leader in collaboration with industry and universities

and has obvious advantages on new technologies related to future hardware needs (information processing, dissemination, storage and display, etc.).NRC-IMS's strategy of working with the Canadian industry is ruling in the dominance of new technologies required in the global IT industry. NRC-IMS industry partners improve technology through research and reduce the risk of industrialization through selective investment technology. If it can be achieved, organization will be in big change in the future and also a good opportunity.The Institute's Photonic Subsystem Research Group focuses on hybrid integrated optical waveguide devices that utilize the benefits of a variety of materials and low cost to achieve comprehensive and optimal functionality on the chip. The group's research include wavelength management systems, silicon/polymer integrated devices, passive/active integrated devices, wavelength integrators, and chemical and biochemical sensors.Based on previous research on waveguides for communication systems, the team's current research focuses on a number of functionally integrated systems including: silicon/polymer hybrid variable optical attenuators (VOAs), arrayed waveguide gratings (AWGs), silicon/ Polymer hybrid thermo-optical switch (TOS), erbium-doped waveguide amplifier (EDWA), tunable multi-wavelength laser source, semiconductor optical amplifier (SOA). These wavelength management systems have a variety of functions including: wavelength monitoring, compensation, blocking, switching, optical add/cancel, optical amplification, decision, light adjustment, optical conversion, reshaping, retiming.At the same time, the team also developed chemical and biochemical sensors that can be used to monitor changes in refractive index and the effects of fluorescence used as materials on the surface of the waveguide.

5.3 Nanoscience Laboratory, Department of Physics, University of Trento, Italy

The field of research in the Nanoscience Laboratory of the Physics Department at University of Trento in Italy involves the following three aspects:(1) Nano-photonics: Photons in the nanometer range can be new phenomena which can bring new devices. Research on nano-crystalline semiconductors has enabled new ways to fabricate devices such as amplifiers and lasers. Two-dimensional and three-position photonic crystals can be fabricated by electron beam lithography. Integrated silicon optoelectronics focuses on optical switches, modulators and shutters. The combination of nanocrystalline materials and photonic crystals enables the development of new devices for biosensors and bioconverters.(2) Characteristics of nanomaterials: Materials with new functions such as ionic compounds or semiconductors are mainly used for energy, microelectronics and optoelectronics. Among various materials, nanostructured materials have new properties that depend on structural development. For many years, we have been experimenting with nanostructured compositions using wave spectroscopy (Raman and FT-IR), mainly quantum dots of nanostructured metals, dielectric oxides or semiconductors. Recent research has also involved carbon nanotubes.(3) Nano-biotechnology: The main goal of this direction is to research and test new nanodevices designed to reach atomic levels and control their three-dimensional structure to

master their performance. The peculiarity of these properties is that they are biomolecules that self-regulate three-dimensional structures, and the addition of nanostructured molecular organisms, such as quantum dots, enables access to new levels of nanodevices, for example nanosensors, nanoconverters, and nano-optical flip-flops. This research is a collaboration between biochemists, materials scientists and electronics engineers. We are currently working on silicon-based optical nanosensors for identifying pathogen types (viruses and DNA) and tiny systems.Professor Lorenzo Pavesi, a well-known semiconductor optoelectronics expert in the laboratory, is an internationally recognized authority on silicon-based optoelectronics research. He has published important papers in internationally renowned journals such as NATURE and has organized many international conferences on silicon-based optoelectronics.

5.4 Intel

Intel has divided the research of silicon optoelectronics into three stages. There are six major problems: light source, optical waveguide, optical modulation, light detection, low-cost integration, and intelligence. As shown on the picture.

The first stage is to demonstrate the ability of silicon as an optical material, and Intel's research on silicon optoelectronics is the first stage. Silicon has the performance of making active and passive optical devices, but performance is limited when used as an active device. These properties have been improved through research before being made

into a multi-function integrated optical module. Intel put most of its energy into active devices, such as light adjustment, detection, switching, modulation, and amplification, and achieved some results, including the first Gbit-rate modulator and the first continuous-wave silicon laser. Although 10 Gbit/s modulators made of LiNbO3 (lithium niobate) and InP (indium phosphide) have been widely used today for long-distance communication, no silicon technology was used to make module which speeds exceeding 20 Mb/s before 2004. In February 2004, Intel announced the successful development of a Gbit/s silicon light modulator. By integrating devices like transistors, Intel is able to make light modulators faster than ever before. A year later, Intel researchers confirmed that their optical modulators have reached a transfer rate of 10 Gbit/s.In the past, silicon lasers were not developed because of the semiconductor properties of materials. Photon excitation and even optical amplification can be replaced by InP materials. Intel researchers have discovered that Raman scattering can make light waves pass through silicon for amplification, which is based on the "pump" light produced by the crystal transfers energy to the signal light. However, the question is how to maintain continuous work. Due to the chaotic quantum effect known as "two photon absorption", the cloud of light absorbing electrons is concentrated in the amplifier.

By integrating diode-based semiconductor devices, researchers have found that they can clear electron clouds for continuous operation. By placing a mirror around the optical amplifier (at the end of the chip), Intel built the world's first continuous wave silicon laser.After developing a number of compelling active optical devices, the silicon optoelectronics research team hopes to enter the second phase of hybrid integration despite the difficulties described above. The second phase begins with a silicon optical test rig, which is a silicon gathering platform that assembles electrons and photons into a micromechanical structure. The silicon structure is capable of guiding the device in a reasonable position without the need to turn on the light source. At this stage, Intel will directly integrate some specific functions into silicon devices. For example, silicon optical multiplexers and detectors can be integrated into multiple receivers or silicon modulators, and lasers and passive components can be integrated into multiple transmitters. It is only used when the integration solution benefits the final module, including performance improvements, smaller size, and lower cost.The final stage of research is a monolithic silicon integrated circuit, in which all devices are integrated into one module, so that there is no need to process any light from the source before use, and the cost is much lower. At the same time, it can bring about the benefits of electronics. If optoelectronic integration can be solved, it is also a revolution in the field of electronics.If the cost is low enough, new products will follow. The integrated silicon optical transceiver can be directly integrated into the connector of the optical cable to complete the function of the electrical interface. For the technician, this is like a single cable, placing all the sensitive optical interfaces in the connector. Network devices such as server blades only need to have an electrical interface. As for the electro-optic conversion, it is obviously possible to complete the cable itself. If the connection fails, replace the cable.A large number of silicon optical chip integrations can transform the connection between the system and the network into optical interconnections. As mentioned earlier, the use of optical transmission eliminates bandwidth and distance constraints, and the soft structure enables more efficient data transfer. The application of silicon optoelectronics is beyond the scope of digital communications, including optical debugging of high-speed data, extending wireless networks by transmitting analog RF signals, and low-cost lasers for biomedical applications.

5.5 Luxtera

Luxtera was founded in 2001 and was the first company to offer a photonic device solution. At the beginning, Luxtera was one of the world's leading companies producing small line-of-line CMOS process chips. Luxtera's CMOS photonic devices are integrated by CMOS electronics processes and are smaller than traditional photonic devices.

Luxtera's products meet the bandwidth requirements by directly integrating high-speed fiber optic optical network interfaces to standard CMOS chips. The product design is not only to transfer large amounts of data from one chip to another (nearly considering distance and bandwidth). To adapt to Moore's law to meet the exponential increase in network data interface data processing.

Historically, the line spacing of silicon has continued to decrease following the Moore's law proposed by Gordon Moore in 1965. This silicon manufacturing process is an order of magnitude higher, enabling chips with billions of transistors to be processed at speeds up to GHz. However, the inherently infinite data processing power of the chip is increasingly limited by the chip I/O speed, because the chip I/O speed cannot be increased by Moore's law, the silicon processing speed and the integration density are surprisingly increasing, and the electrical characteristics of the interconnection. The limitations make the existing ones unable to meet the bandwidth requirements of future silicon products. Luxtera's CMOS photonics technology platform will meet these challenges.

Luxtera's CMOS photonics technology enables the construction of complex optical systems using CMOS process products. The same CMOS process is currently used to fabricate very large scale integrated circuits (VLSI). Combining high-speed digital circuitry, communications and sensing products for a wide range of discrete computer passes, Luxtera designs, fabricates and tests a complete set of photonic components.

5.6 VLINK Optics Corporation

VLINK Optics is a high technology company focusing on developing, manufacturing and selling silicon photonics fiber connectivity and micro/short fiber jumper used on 40G, 100G and 400G high speed transceiver modules, including

SR4 MT-MT jumper, PSM4 MT-FA jumper, MT-FA for grating coupling or edge coupling of silicon photonics package, TFF CWDM4/LAN WDM or PLC CWDM4/LAN WDM subassembly High PER Polarization-Maintaining devices

VLINK keep integrating advanced technologies and resources, trying to be an innovator and explorer on the field of fiber optics micro connection on high speed modules. VLINK provide customer fiber optics micro-connection solutions of inter-connecting in high speed modules with compact size, low power consumption, cost effective and quality guarantee.Under the background of the continuous maturity of silicon photonics technology, the interface scheme derived from the silicon optical coupling scheme has become a new research direction. VLINK has been deeply researching the extension application of silicon photons and the development route of future technologies and has developed various technical solutions which greatly shortens the development cycle of the customer. The products mainly include 90° Bending FA for grating coupling and MFD Matching for edge coupling, etc.

90deg MT-FA for Grating Coupling

6. SUMMARYWith the breakthroughs progress in silicon-based photonics in recent years, silicon-based photonics has gradually become practical, and silicon is no longer suspected as an optical material. Instead, it is beginning to seek ways to use this revolution technology.1) Ordered silicon-based nano-quantum dots with small size and high density are the most

promising active region materials for achieving high-strength, high-stability and high-efficiency luminescence of silicon-based nanostructures. However, in order to realize the true silicon-based nano-quantum dots, more tentative research is still needed in terms of growth mechanism, process technology and performance detection.

2) In all the research of silicon-based optoelectronic integrated devices, silicon lasers are the most important. Further research is needed to optimize the combination of gain material type, device structure form and electro-excitation mode.

3) As a variety of silicon-based optical waveguide structures and devices that function as optical transmission, optical switching, and optical modulation, to achieve their strong limiting effect on the optical field, low transmission loss, high coupling efficiency, fast response speed, and low insertion loss. In addition, it is necessary to conduct in-depth exploration in the design of the waveguide layer and the confinement layer material, the waveguide structure, and how to facilitate the integration of silicon-based optoelectronics.

4) While studying the design and fabrication of silicon-based photonic integrated devices, relevant basic theoretical research should be further strengthened. For example, clarification of the luminescence, stimulated radiation, light transmission and photodetection properties of silicon-based materials and the relationship between material type, structural characteristics, electronic structure and carrier transport, and the intrinsic mechanism of the Raman effect.

It takes a certain amount of time for photonic technology to replace electronic technology. In addition to technical difficulties, the current cost of photonic technology is also an important reason. Dr. Rong Haisheng, a senior scientist at Intel's Photonics Technology Lab, is cautiously predicting that the cost of both will be roughly the same in about 10 years, and it will be a turning point in the complete replacement of electronic technology by silicon-based

MFD Matching FA for Edge Coupling

photonics technology. Once silicon-based photonics technology achieves its practical goals, its high bandwidth, high rate, and low interference characteristics will revolutionize inter-chip interconnect and back-floor cabling technologies and will revolutionize the communication speed and bandwidth of today's computer systems. Behind the current state of computing chip processor speed, which led to a new technology revolution. Following the world's leading silicon photonics companies, VLINK Optics Corporation continues to develop micro-connected products that meet the needs of these customers and contribute to silicon photonics technology and industry to scale.