Planar optical waveguide technology and its device developme

Passive planar optical waveguide devices, as the name suggests, do not need energy (electrical) source devices are passive devices, only as light wave signal transmission, wave division/wave filtering and other functions. It mainly includes planar optical waveguide splitter, array waveguide grating (AWG), optical filter and so on. At present, the planar optical waveguide splitter is very popular in the domestic and international market, according to the report of the market and technology consulting company ElectroniCast on April 5, 2016, the total global planar optical waveguide splitter market reached 696 million US dollars in 2015, an increase of 14%. China has now become the dominant player in the planar optical waveguide splitter market, accounting for more than 35% of the total market. Before 2012, the domestic optical splitter devices were all imported from South Korea and Japan, and the domestic can only do packaging, and most of the profits were taken away by South Korea, Japan, Europe and the United States. After years of dedicated research and development, after 2015, Henan Shijia Photonics has become the world's largest optical splitter chip supplier, with a monthly production of up to 3,000 6-inch wafers. At present, there are no less than 100 domestic enterprises specializing in packaging and manufacturing of planar optical waveguide splitters.

 

AWG is a key component of WDM (wavelength division multiplexing/demultiplexing) system, and its design and manufacture are more difficult than planar optical waveguide devices. At present, there is no large-scale production in China, and it is still in the stage of mass production. At present, using the series AWG filtering structure, the channel interval can reach 10GHz (wavelength interval 0.08nm), and the channel number is more than 1000. Commercial AWG is typically 100GHz (wavelength interval 0.8nm).

 

The active planar optical waveguide device refers to the optical waveguide device that requires an energy (electrical) source to work, and can be used as the generation, regulation, amplification and detection of optical wave signals. It is manufactured from Ⅲ-Ⅴ semiconductor chemical materials. Major semiconductor lasers (LD), optical detectors (PD), optical waveguide amplifiers (OSA), tunable optical attenuators, etc., can be monolithic or integrated, Infinera is the technology and industry leader in such devices. FIG. 2 shows the integrated passive planar optical waveguide device, which has a complex manufacturing process and requires MOCVD (metal vapor deposition). Such products are more developed in Europe, the United States and Japan, and domestic production can only be less than 10G products, and high-end products all rely on imports.

 

Passive/active hybrid integrated planar optical waveguide device. Passive devices and active devices have different materials, and their manufacturing processes are not the same. Recently, SiO2 or Si has been used to make optical waveguide loops, and then PD and LD are mixed together in the way of flip or mount, as shown in Figure 3.

 

Silicon photonic integration

 

There are many kinds of materials used in optical waveguide devices, silica and glass, ⅲ-V compound semiconductors (GaAs and InP), lithium niobate and lithium tantalate, organic polymers, silicon and germanium semiconductors, so there are many kinds of devices. Can optical waveguide devices, like the integrated circuit industry, only use silicon as a material? Because the medium as a laser requires a direct band gap to laser, and silicon is an indirect band gap. Therefore, since the beginning of the development of optical fiber communication technology, the development of its devices can not always be like the development of integrated circuits, can achieve large-scale, ultra-large-scale integration, but only a few, dozens, several functions of integration, can do hundreds, thousands of numbers or functions of integration is extremely difficult.

 

Silicon-based integrated circuits have evolved to the point of near-perfection, and CMOS processes have been perfected. Can the photonic device and CMOS process be combined to make the photonic device material unified and achieve large-scale integration? Intel and IBM as early as the beginning of this century began to focus on the development of silicon chip optical signal generation and processing technology, has broken through silicon-based photon modulation and detection technology. In July 2007, Intel researchers achieved a silicon laser modulator with a bandwidth of 40Gbps, and in May 2008, an 8-way silicon modulator achieved 200Gbps. In May 2015, a silicon-based optical detector with stable gain in the bandwidth of 10~40Gbps and guaranteed gain bandwidth product above 300GHz was realized.

 

Silicon-based lasers are weak. In September 2006, Intel Corporation and UCSB (University of California, Santa Barbara) jointly released the world's first hybrid silicon laser manufactured in a standard CMOS process, and seven years later, the team demonstrated a hybrid silicon-based laser with speeds of up to 1000Gbps. So far, Raman scattering is the only feasible method for generating lasers in silicon materials, and in 2004, the first silicon-based laser with stimulated Raman scattering effect was demonstrated, followed by continuous Raman scattering lasers in 2005. If the silicon-based laser technology has been comprehensively solved, the silicon-based amplifier will also be comprehensively solved, then the comprehensive silicon-based CMOS technology can be realized, and the optical fiber communication technology will be developed in front of it, as shown in Figure 4.

 

Planar optical waveguide technology and its devices are the key technology and core devices to comprehensively improve information technology, and the key to measure a country's skill level and ability.