Press Release: New collimation module for single-mode diode bars utilizes brightness and beam quality
Aachen, January 2018. Premiere at the SPIE Photonics West: Micro-optics for high-power diode lasers.
New collimation module for single-mode diode bars utilizes brightness and beam quality. Monolithic micro-optics structured on both sides open up new markets for diode-laser manufacturers.
At the “Photonics West 2018”, INGENERIC for the first time presents the new micro-optics module “C-SMDB”, developed by the company for the collimation of single-mode diode bars. This helps to exploit the improved brightness and open up new fields of application for laser manufacturers.
Single-mode bars can achieve high performances with their large numbers of single emitters. Also, the beam quality from single emitters is superior to that of broad stripe emitters, as each emitter gives off light in fundamental mode. To make best use of these advantages, an optical module needs to collimate the light beam separately for each emitter. The emitters are tightly packed, so it is necessary to use compact micro-optics with the finest structures. The new collimation module optimizes the utilization of the high performance available from single-mode diode bars, and this opens up potential new applications.
The new monolithic cylindrical lens array “C-SMDB” from INGENERIC for single-mode bars achieves high degrees of collimation as it is produced with the process of precision glass molding. The array is effectively double-sided: The entry side collimates the slow axis, the exit side the fast axis of the emitted light.
The production accuracy of the micro-optics is subject to considerably higher demands than is the case with the optics for diodes with broad stripe emitters. The pitch between the individual lens elements on the slow-axis side, for example, must be maintained with extreme accuracy: For 200 elements, the pitch has to be on average less than 5 nanometers. The center thickness should ideally be in the range of +/- two microns in order to achieve an optimal result.
INGENERIC uses the precision glass molding of the arrays to meet this challenge, a process which the company uses for other micro-optics in its product portfolio. With glass molding, high refractive-index glass very precisely takes on the shape of the pressing tool. The molds manufactured by INGENERIC to sub-micron precision enable the arrays to be produced with exceptionally high accuracy and reproducibility. INGENERIC successfully manufactures arrays with minimal transition zones, highest filling factors and minimal pitch errors, even in large batches.
Dr. Stefan Hambücker, Managing Partner of INGENERIC, sees great potential for diode lasers: “For the single-mode bars, we are currently working to demonstrate their functionality and cost-effectiveness in new fields of application. That is why, in terms of optics, we are working very closely with the manufacturers of diode lasers. With high fill factors, excellent utilization of the surface area, extremely high contour accuracy and a good orientation of the surfaces to one another, the C-SMDB is exactly the right product to make the best use of the brightness.”
The new array has a design wavelength of 970 nm. The effective focal length (EFL) of the fast-axis collimation (FAC) is 600 μm with a numerical aperture of 0.8, the EFL of the slow-axis collimation (SAC) is 190 μm, and the pitch of the SAC is 48 μm. There are 200 lens elements on each part. The result is a back focal length (BFL) of 179 microns.
beamPROP beam shaping optics
INGENERIC is also exhibiting the beamPROP 200 beam-shaping optics, a lens array that adjusts the beam parameter product (BPP) of the fast and slow axis of high-power diode lasers. It is a key component for fiber coupling of diode bars and for dense wavelength multiplexing (DWM).
What is new is that INGENERIC now produces arrays with pitches not only of 500 and 400 μm, but now also with a pitch of 200 μm. This allows the emitters on the bars to be placed closer together and provides an increase in the usable power, which is a necessary step to increase the efficiency in the application. As a result, the beamPROP 200 and the C-SMDB extend the spectrum of diode laser applications.
Christian Wessling, Head of Product Development at INGENERIC, sees the company as a trailblazer for new applications: “With regards to the DWM, which operates with the beamPROP, a number of manufacturers of diode bars continue to work on a comprehensive concept—and optics are a crucial component here. We are working with them step by step to develop this technology. We see ourselves as enablers who are helping to open up new applications.”
INGENERIC at “SPIE Photonics West” – San Francisco/USA, Jan. 27 to Feb. 1, 2018 – Stand 5153
Background information on the industry trend
Diode lasers are characterized by their compact design, high efficiency, long service intervals, and long service life. Although the diode laser is already qualified for numerous applications, the achievable brightness is still subject to the structure of the component as the limiting factor. Also, beam quality today is still not sufficient for some applications, such as material processing.
Manufacturers of diode lasers are endeavoring to develop new fields of application for their products. Primary factors are the brightness and beam quality of the diode lasers. All current developments aim to improve these properties, for example to stabilize the wavelengths during multiplexing (DWM) and thus to combine higher powers with thinner fibers, or to make optimum use of the brightness of single-mode bars. Both approaches require special micro-optics for collimation and beam shaping. However, development work is still required in comparison to the established designs that rely on FAC, SAC, deflecting mirrors and coupling optics to bundle the power into a single fiber. The new micro-optics from INGENERIC have the potential to outperform the brightness of established approaches, which would open up new applications.
Dr.-Ing. Uwe Stein