Anritsu develops one-watt lasers at 14xx nm
The use of a longer laser cavity length is very effective to increase the output power of laser diodes due to better heat dissipation and lower resistance of the diode. However, since the internal loss in conventional diodes is relatively high, power efficiency is reduced when the cavity length increases. Consequently, an excessively high current is necessary to obtain a high output power.
Anritsu s new high-power laser diode employs an asymmetric cladding layer structure with InGaAsP, which has a high refractive index, as its n-cladding layer. The p-cladding layer is InP. This new structure minimizes absorption loss in the p-side cladding layer, which is main cause of internal loss, by shifting the guided wave field distribution in the laser cavity to the n-cladding direction.
This structure also enables widening the active layer, resulting in a decrease in the diode resistance. As a result, both increased efficiency and reduced drive voltage can be achieved at the same time. Moreover, the device has a narrower emission beam divergence angle than conventional lasers and an almost circular beam shape, which facilitates high-efficiency coupling to the single-mode fiber.
As the result of adopting this structure, the internal loss is two-thirds that of a conventional diode, while power efficiency increases greatly. For instance, a comparable diode with a conventional structure consumes 5.1 W to obtain a 500 mW fiber output, whereas, Anritsu s new diodes reduce the power consumption by 35% to 3.3 W. A maximum output power of more than 1 W was obtained for a 3-mm-long chip – the company claims this is the world s highest-level output.
A single unit using the new diode can provide the required output power that used to be supplied by coupled outputs from two conventional pump laser modules. It can also decrease the number of drivers and optical components to allow lower total system building cost. In addition, application of the new devices to fiber-sensor light sources including strain sensors, which requires a high output power, is also expected.
