A single frequency laser system is configured with an elongated housing extending along a longitudinal axis and having opposite axially spaced upstream and downstream ends. The housing encloses a laser chip configured to emit a radiation which propagates along a light path and emitted through the downstream faucet thereof. One or more spaced frequency discriminators are mounted in the housing downstream from the chip so as to define an external resonant cavity with the upstream faucet of the of the laser chip. At least two or more separate thermoelectric coolers ("TEC") are mounted in the housing to affect the chip and discriminators so as to the output of the system at the desired frequency.