Wavelength-stabilized diode laser
A hybrid external cavity laser (HECL) system comprises a diode laser, collection and collimation optics, and a volume Bragg grating, emits radiation at a single wavelength with a short-term wavelength stability in the order of at least one part in a billion The wavelength stability is achieved by use of a thermal management system, comprising inner and outer housings, each containing a temperature sensor, and electronic circuitry that monitors the temperatures and controls both the laser diode current and a thermoelectric cooler based on temperatures determined from said temperature sensors. The laser system is packaged in a compact enclosure that minimizes waste heat, facilitating use in applications that have heretofore employed stable, single-frequency lasers, including He—Ne lasers.
1. A device for emitting laser radiation having a stable wavelength, the device comprising:
a thermally conductive first housing containing:
a hybrid external cavity laser comprising:
a diode laser having a known emission wavelength;
optics collecting and collimating the known emission wavelength; and
a volume Bragg grating optical component partially reflecting the collected and collimated known wavelength;
a first temperature sensor proximate the diode laser;
a thermally conductive member in thermal contact with the hybrid external cavity laser and the first temperature sensor at a first surface and in thermal contact with the first housing at a second surface;
a thermally conductive second housing enclosing the first housing, the second housing comprising:
a thermoelectric cooler in thermal contact with said first housing and the second housing; and
an opening, optically aligned to an opening in said first housing, allowing said known emission wavelength to exit said second housing;
a second temperature sensor and an electronic circuitry mounted on a circuit board in thermal contact with said second housing, said electronic circuitry:
receiving a temperature measured by at least one of the first temperature sensor and the second temperature sensor, said temperature being associated with a temperature of said diode laser and said electronic circuity, respectively, and
controlling operation of the diode laser and the thermoelectric cooler, wherein the electronic circuitry controls:
a laser drive current provided to said diode laser to cause said diode laser to emit said known wavelength; and
a temperature control voltage applied to said thermoelectric cooler to maintain said diode laser at said known emission wavelength.
2. The device of claim 1 , wherein the emission wavelength is between about 375 nm and about 3 μm.
3. The device of claim 1 , wherein the emission wavelength is between about 630 nm and about 650 nm.
4. The device of claim 1 , wherein the first housing is a TO package.
5. The device of claim 1 , wherein the first housing is a butterfly package.
6. The system of claim 1 , wherein the thermoelectric cooler is contained within the first housing.
7. The device of claim 1 , further comprising:
a memory storing a laser drive current for each of a plurality of measured temperature values.
8. The device of claim 7 , wherein said measured temperature values are temperature values associated with at least one of said first temperature sensor and said second temperature sensor.
9. The device of claim 1 , wherein the first housing is at least in part thermally insulated from the second housing.
10. The device of claim 1 , wherein the electronic circuitry includes a microcontroller.
11. The device of claim 1 , wherein the electronic circuitry includes a voltage reference source.
12. The device of claim 1 , further comprising:
a third housing enclosing said second housing; said third housing comprising:
an opening, optically aligned to said opening is said second housing; and
a third temperature sensor in contact with said third housing; and
electronic circuitry:
receiving a temperature measured by said third temperature sensor.
13. The device of claim 1 , wherein said temperature control voltage applied to said thermoelectric cooler is based on said monitored temperatures of at least one of said first temperature sensor and said second temperature.
14. The device of claim 1 , wherein said diode laser drive current is predetermined.
15. The device of claim 1 , further comprising:
input means for inputting initial operating conditions for said laser diode.
16. A method, operable in a processor, for determining a temperature setting of a laser diode, the method causing the processor to execute the steps comprising:
setting an operating temperature of said laser diode;
varying a temperature surrounding said laser diode in a series of known step sizes;
measuring a wavelength of said laser diode for each of said known step sizes;
determining a temperature compensation factor at each of said known step size;
determining a difference in wavelengths between a current step taken at a current temperature and a previous step taken at a previous temperature; and
setting a new operating temperature based on said determined temperature compensation factor when said difference is greater than a known threshold; and
retaining the operating temperature when said difference is less than said known threshold,
by determining a power to maintain said set operating temperature; and
applying said determined power to a cooler.
17. The method of claim 16 , further comprising:
storing said determined temperature compensation factor at each of said known step sizes.