For a decade now, Photodigm has worked with leading researchers worldwide to deliver monolithic, single frequency laser diodes for the most demanding requirements.Our laser design and wafer fabrication engineers have consistently improved the performance of our devices. During this time, our users have seen higher powers, lower threshold currents, and higher slope efficiency compared to earlier generations of product. Users are reporting Gaussian linewidths below 500 kHZ, comparing favorably with commercial ECDLs and almost an order of magnitude lower than competing DFB lasers. With the introduction of our advanced Mercury™ TOSA in 2012, shown in Fig. 1, Phogodigm lasers set the standards for spectroscopic laser diodes for research and industry.
Fig. 1. The Photodigm Mercury™ TOSA with flex cable, right view. Left, Mercury TOSA mounted in a heat sink for use in a laboratory environment.
A consistent request from our customers has been to deliver a more user-friendly beam. The free-space beam from a Photodigm DBR laser exhibits modest astigmatism and a rapidly diverging fast axis. This is typical of almost all semiconductor lasers and is a result of the epi design and the ridge waveguide design. Responding to these inputs, Phogodigm has developed a virtual point source (VPS) lens, specifically designed to correct the astigmatism and reduce the divergence of the fast axis. This proprietary micro lens is mounted on the submount, as shown in Fig. 2, and contained within the Mercury TOSA. The resulting free-space beam exiting the TOSA is a near-Gaussian, slightly diverging, slightly elliptical beam that can be focused or collimated as needed with a single asphere, as seen in Fig.3
Fig. 2. VPS microlens precisely aligned and mounted on the submount with Phgodigm DBR laser.
Fig. 3. Free space beam profile measured after a single collimating lens with 8 mm focal length. The choice of an asphere is determined by the requirements of the user. The raw data and Gaussian curve fit exhibit 95% overlap.
Available now in the Mercury™ TOSA