For interferometry applications of optical metrology the circuitry can be placed on a PIC, allowing for a capact and stable device.
As an application demonstrating how PICs can be used in corporation with free-space optics, a fringe pattern generator is developed. As the phase of the visible light can be controlled very accurately on the PIC, adjustable fringe patterns can be made and projected on a surface. The example shows the principle of a simple two channel version. But the principle can be extended to more channels, allowing even more flexibility in the number of fringes and the fringe shape and pattern.
The Integrated Laser-Beam Combiner combines up to eight visible wavelengths between 405 and 680 nm. The combining is polarization maintaining and the combiner can be assembled with polarization maintaining fibers.
The ILBC is a compact and robust module that can be extended with different functions like:
- an integrated power tap enabling powermonitoring functionality in the combined output signal.
- the integration of intensity control function on the input channels, allowing full control over the combined output wavelength combination.
- adding a spatial switch at the output of the combiner, creating multiple output positions of the combined signal.
By combining a VOA building block, together with a power splitter (acting as a power tap) an o chip Laser stabilization circuit can be made.
The Variable Optical Attenuator (VOA) for visible wavelengths enables to decrease the output power of a lasers, while the lasers operate at high output powers. This increases the stability of the total system as the lasers prefer operation at their “sweet-spots”, which typically are high power. However for many applications these higher powers can damage the biological or medical samples. Lowering the power of the laser directly however, increases the noise as the laser no longer operates at its preferred operation point. The VOA for visible wavelengths offers the possibility to run any laser at its preferred output state and the output power can be adjusted to match the desired levels of a measurement.