Vertical cavity surface emitting laser with optimized linewidth enhancement factor

1. A method for making an electrical device that includes a vertical cavity surface emitting laser (VCSEL) suitable for self mixing applications, comprising:

selecting an operating temperature for a VCSEL to be incorporated into the electrical device;

selecting a laser doppler velocimeter comprising the VCSEL and being configured to measure movement of an object relative to the VCSEL, wherein the VCSEL comprises:

a bottom DBR mirror formed on a substrate;

an active region formed on the bottom mirror;

a top DBR mirror formed on the active region;

contacts electrically coupled to the active region; and

the VCSEL having a T 0 where T 0 is defined by the temperature at which a threshold current of the VCSEL is at a minimum and wherein the VCSEL is selected so that the T 0 is greater than the selected operating temperature; and

incorporating the laser doppler velocimeter into the electrical device and configuring the electrical device such that the VCSEL operates at the selected operating temperature, thereby making the laser doppler velocimeter sensitive to light reflected back into the VCSEL.

2. The method of claim 1 , wherein at least one of the bottom DBR mirror, the top DBR mirror, the contact, a trench, and an aperture are optimized so as to make the VCSEL more sensitive to light reflected back into the VCSEL.

3. The method of claim 1 , wherein at least one of the bottom DBR mirror, the top DBR mirror, the contacts, a trench, and an aperture are formed so as to make the VCSEL more thermally sensitive to changes in current through the VCSEL.

4. The method of claim 1 , wherein the electronic device is an optical mouse.

5. The method of claim 1 , wherein the electronic device is a telephone handset.

6. The method of claim 1 , wherein the electronic device is a paper positioning device.

7. The method of claim 1 , wherein the electronic device is a linear measurement device.

8. The method of claim 7 , wherein the linear measurement device is configured to measure a length of fish tape.

9. The method of claim 1 , wherein the electronic device is incorporated into an appliance.

10. The method of claim 1 , wherein the top DBR mirror has alternating layers of binary semiconductor materials and the lower DBR has alternating layers of ternary semiconductor materials.

11. The method of claim 1 , the top DBR mirror has higher aluminum content compared to the aluminum content in the bottom DBR mirror for a given distance away from the active region.

12. The method of claim 1 , wherein VCSEL comprises a trench formed below the active region.

13. A method for making a sensor, comprising:

designing a VCSEL comprised of a substrate, a lower DBR mirror, an active region, and an top DBR mirror, the VCSEL having a T 0 where T 0 is defined by the temperature at which a threshold current of the VCSEL is at a minimum with respect to temperature, the designing of the VCSEL including,

selecting a design operating temperature for the VCSEL;

identifying that the VCSEL will be used in a self-mixing application at a the design operating temperature; and

optimizing the VCSEL for the self-mixing application by determining a composition and configuration of the VCSEL that gives the VCSEL a T 0 that is higher than the design operating temperature.

14. A method as in claim 13 , further comprising forming a sensor comprising the design VCSEL of claim 13 , the VCSEL having a T 0 greater than the design operating temperature and the sensor being configured to measure movement of an object relative to the VCSEL using laser Doppler velocimetry.

15. A method for determining the movement of an object, the method comprising using a sensor as defined in claim 14 to measure movement of the object relative to the sensor, wherein the movement is determined using laser Doppler velocimetry.