Nextreme Demonstrates Laser Cooling For TO-Can Packages

Laser diodes are susceptible to heat, which can adversely affect their output power and wavelength. Manufacturers have traditionally used thermoelectric coolers for temperature control. However, as the photonics industry has moved to smaller, more integrated packaging in order to reduce costs, conventional TECs have not kept pace with these size and heat requirements. Because of this, in some instances designers have chosen to place the cooling device outside the package. Cooling the diode by cooling the entire package is an inefficient method of thermal management.

Thermoelectric coolers made from thin-films are smaller and thinner than conventional TECs and can be embedded in the smallest of packages. In addition, thin-film TECs have a low mass which enables a more rapid thermal response to changing temperatures.

To illustrate the benefits for cooling a laser with an embedded TEC, Nextreme mounted a laser diode on the active side of an OptoCooler HV14 thermoelectric cooler in a TO-8 package. At 85°C, the OptoCooler HV14 module can pump 1.7 watts of heat in a footprint of less than 3mm2. The TEC can create a temperature differential (ΔT) of up to 50°C between its hot and cold sides. As a part of the demonstration, a test bed was assembled to measure the effects of cooling on laser output and wavelength. When the TEC was turned on, the temperature of the diode quickly dropped from 42°C to approximately 21°C in milliseconds and the output level of the laser nearly doubled from 0.38mW to 0.74mW at a drive current of 100mA. An optical spectrum analyzer measured a wavelength shift toward the blue spectrum of approximately 13.6nm.