UV-RGB: The integrated laser beam combiner

Research group

Prof.dr.ir. A.J. Huis in’ t Veld

Dr.ir. G.B.R.E. Römer

Dr.ir. D.M. Brouwer

Ir. K.G.P. Folkersma (contact person)

Project term

August 2011 – August 2015


Laser forming, fiber alignment, beam combining, precision measurement and control

Project Background

In many applications there is a need for multiple wavelengths of laser light combined into one optical fiber. An optical chip has been developed by XiO photonics that can combine laser light from four sources (from UV up to visible wavelengths) into one beam while maintaining the polarization of the input. Applications for this chip are for example in medial analysis methods like confocal microscopy or flow cytometry, but can also be found in consumer entertainment or food sorting machines. While laser beam combiners exist for a while, they are often bulky and not plug and play. The optical chip however, is small, robust and has optical fibers as in- and outputs, making installation easy.

The ILBC connected to four laser sources.


The UV-RGB project is focused on the problems that arise with the various connections that need to be made between the chip and fibers, and to a pluggable connection between two fiber ends. The alignment of the fibers needs to be more precise when the wavelength gets shorter to get the same insertion loss. For example a lateral offset of the used fibers of 0.5um results in 5% loss for red light, but 15% for blue light. This means that solutions that are widespread in telecommunication fibers (where infrared light is used) are not suitable for the visible spectrum due to the required tolerances.

Focus areas of the UV-RGB project. Encircled by dashed lines.

Current methods use an UV curing adhesive to fix an intermediate body to the chip and to the fibers. After long exposure to leaking UV light from the connection, this adhesive begins to degrade and the connection quality drops. Furthermore this bonding process is hard to control and creep of the adhesives can distort the alignment of the fiber to the chip.

Project Approach

The role of the UT in this project is to find an alternative to the current bonding methods and fiber connections. Due to manufacturing tolerances, passive alignment is unsuitable for the UV and visible spectrum. Currently research is done to investigate the use of laser micro adjustment to create an integrated actuator to position and fix the fiber in after the bonding phase. FEM models of laser adjustment processes have been developed.

Future Work

Experimental research is planned to validate this model. If correct, this model can be used to develop actuator structures that can position the fiber in 5 directions with respect to the chip or opposing fiber. See the figures below

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Concept of integrated actuator:
The fiber is fixed to the actuator “roughly”. The actuator is then deformed by laser adjustment to move it into the correct position and hold it here.

Temperature gradient laser adjusting mechanism:
a: Heating the top of a metal plate with a laser source b: Thermal expansion introduces compressive stresses. c: Due to the decreasing yield stress with increasing temperature, the material deforms plastically at the top. d: When cooling, the result is a bendt plate towards the laser source.

The integrated actuator should incorporate the five directions in this figure.


The project is funded by IOP Photonic Devices

The UV-RGB project is a collaboration of two universities and three companies:


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