Beam combiner for confocal microscope

The project was initiated based on customer demand for a replacement for a worn-out Ar laser used as an excitation source for a confocal microscope (Leica SP5). The Ar laser has several emission lines in the blue-green range (458 nm - 514 nm). The customer's goal was to cover this range and, if possible, to extend it with additional wavelengths.

Another important requirement was the full integration of the lasers into the existing excitation unit of the microscope, i.e., placing the lasers in the appropriate box, which also houses other sources, and ensuring that the new lasers are fully controllable by the existing hardware and software components. The challenge in this case was not only the limited space in the excitation unit, but also the connection to the rest of the system set up for the Ar laser.

We decided to solve the task using a laser beam combiner. This device is specifically designed to combine the outputs of several lasers into a single beam. Given the relatively low power used in confocal microscopy (< 3 mW per sample), we chose compact OBIS diode lasers from Coherent. In the first phase of the project, the customer chose only two wavelengths (488 nm, 594 nm), with the beam combiner allowing for the possibility of adding two more lasers in the future.

The beam combiner was successfully fully integrated into the confocal microscope. The size and design of the box were designed so that it could be inserted into the appropriate place inside the excitation unit and other components (especially power supplies and other accessories) could be mounted on it. The electrical connection was designed so that the lasers could be activated by a dedicated button on the front panel of the excitation unit. The output beam from the beam combiner was connected to a single-mode (SM) fiber leading to the confocal head of the microscope. The wavelength used is selected using the original acousto-optic tunable filter (AOTF), which was calibrated during installation to maximize transmission for the new wavelengths. From the operator's point of view, the beam combiner has fully replaced the original Ar laser without compromising user comfort.

Device parameters

• 2x Coherent OBIS laser (488 nm 60 mW, 594 nm 60 mW)
• 2x free slots for adding additional wavelengths
• Output connection to SM fiber
• Full software and hardware integration into existing microscope
• Can be controlled directly from Leica software + laser management via Coherent Connection application