Installing IR laser to trap biological particles
The optical tweezers setup was transitioned to an infrared laser to work with biological samples. This is necessary because biological systems will absorb the 637 nm wavelength light from the visible laser which in turn damages and kills the samples. Absorption of IR light does not occur, and therefore the same systems will be unharmed by the IR laser.
CAUTION: Always use the appropriate eye protection when operating this laser! It can cause permanent damage if proper safety precautions are not taken!
A 980 nm wavelength single mode fiber laser was used in a similar fashion as the 637 nm laser. To install, the fiber was connectorized to enable coupling into an infrared fiber collimator. Additionally Newport temperature controllers and laser diode drivers were installed to safely monitor the use of the IR laser. To operate, first stabilize the temperature controller at 20 degrees Celsius. Next, the current through the laser diode can be adjusted using the diode driver controller. It is recommended to use a power meter to determine a Power vs. Current relationship in order to establish a safe working range for the a laser. Finally replace the necessary optics in the system so that they are compatible with 980 nm wavelengths.
Aligning this laser is more difficult because it is not visible to the naked eye. Getting the system well aligned with the 637 nm laser is beneficial, and then using an IR card and IR viewer are extremely helpful to seeing the beam. Again, be safe when initially working with the IR beam because it could be scattering off of various surfaces in your system.