A new solution to one of the most troubling challenges of semi-conductor industry has been introduced in the form of minute, high-performing lasers cultured on silicon wafers. Such limitation held back then integration of electronics with photonics on a silicon platform, till date. It is a great breakthrough for the semiconductor industry as it was more than 30 years from now that the crystal lattice of laser materials and silicon could not match up, making the integration of two materials quite impossible.
A team of scientists from Hong Kong University of Science and Technology and the University of California, Santa Barbara – Sandia National Laboratories and Harvard University were able to culture minute lasers directly on silicon, which is a massive breakthrough for semi-conductor industry.
As reported by the group, they were able to integrate the sub-wavelength cavities into silicon platform to generate and execute high-density-on-chip light emitting elements, which are the essentials of their tiny lasers.
For this, they first resolved silicon crystal lattice troubles to a level where the cavities were vitally equivalent to those fabricated on lattice-matched gallium arsenide (GaAs) substrates. Nano-patterns fashioned on silicon to reduce the defects made the GaAs-on-silicon template almost defect free and substantial detention of electrons within quantum dots introduced on this template made lasing possible.
The team was then able to utilize optical pumping, which is a process that uses light instead of electric current to pump electron from a lower energy level in a molecule or atom to a bigger level to symbolize that devices can operate as lasers.
“Placing lasers on microprocessors augments their efficiencies and allows them to move at much reduced powers, which is a major step toward electronics and photonics integration on the silicon platform,” says Professor Kei May Lau, Department of Electronic and Computer Engineering, the University of Hong Kong of Science and Technology.
Conventionally, the lasers employed for commercial applications are quite big – typically 1 mm x 1mm. Small length lasers tend to suffer from the loss of big mirror. But the researchers were successful to combat this challenge with “tiny whispering gallery mode lasers – only 1 micron in diameter – that is 1,000 times shorter in length and 1 million times smaller in the area as compared to those presently used,” says Lau.
Lasers of whispering gallery mode are well-thought-out as an attractive source of light for on-chip optical communications, chemical sensing, and data processing applications.
“Our lasers possess low threshold and are equivalent to the measurements required for integrating them into a microprocessor,” highlights Lau. “And such minute high-performing lasers can be cultured directly on silicon wafers, which is what almost every semiconductor chips or integrated circuits are fabricated with.” As till now, these tiny lasers on silicon are suitable for high-speed data communications.
Conclusion – “Photonics is the most cost-effective and energy-efficient way of transmitting large big volumes of data over long distances. Till now, ‘off chip’ were the only laser light source for these applications, but our research work is an indispensable component, majorly of microprocessors and silicon photonics,” says Lau.