Quantum Dot Lasers Now Reality

In recent research I conducted for the Optical Interconnect report I wrote for CIR, I found some encouraging news on quantum dot lasers. Measuring 20nm in diameter, a quantum dot (QD) is defined as a semiconductor whose electrons are confined in all three spatial dimensions. As a result, it has properties that lie somewhere between those of bulk semiconductors and those of discrete molecules. QDs have been studied for a wide range of applications such as transistors, solar cells, displays, medical imaging, optical amplifiers, sensors, drug delivery and light emitters (both LEDs and diode lasers). QDs also could be used as the physical "incarnation" of qubits in quantum computing R&D and in quantum encryption systems. All of these applications are based on the fact that QDs are zero dimensional, which gives them superior transport and optical properties. They also need very little power.

QD Laser, a Japanese firm backed by Fujitsu Limited, Mitsui Ventures and Mizuho Capital Co., Ltd, announced what I believe is the first commercially viable QD laser in March 2009. Since then, it has added several products to its portfolio. They include FP/DFB laser chips, TO-can and TOSA and wide-band SOA butterfly components. The lasers have capability to run at data rates up to 10 Gbps. These devices are well suited for datacom and telecom equipment.

It seems that QD lasers may have future applications in chip-to-chip optical connections. They may also have applications outside of telecom in sensors and in future quantum encryption/quantum computing systems. In addition to QD Laser's devices, Taiwanese researchers have built tunable QD VCSELs. Also, VI Systems (VIS), a German-based start-up, is working on QD-enhanced VCSELs. This components company has recently received substantial funding and we note that at recent industry conferences VI Systems presented a paper on 25-Gbps VCSELs that were rendered temperature insensitive with the use of QDs. VIS has recently released a product catalog of TOSAs, ROSAs, VCSELs, PINs, arrays, TIAs, VCSEL drivers and high-speed test boards that utilize its technology. Its products are suitable for 850nm 25G and 40G operation. It seems as though this may be one of the only currently viable solutions for stable operation of VCSELs beyond 10G.