Silicon Optics with Large Sag

Xi'an, China  – Focuslight Technologies Inc., a global provider of high-power diode lasers and micro-optics, has announced Silicon Optics with Large Sag.

Silicon optics have been widely used in a variety of infrared applications operating in the 1.2 - 7 μm wavelength range such as NIR imaging, biomedical and radiation sensing, with the advantages of high refractive index (n=3.4), hard material resistance, and low temperature sensitivity.  Due to its low density (2.329 g/cm3), silicon optics are ideal for weight-sensitive applications.

The typical processing technologies of silicon optics are etching or CNC machining, resulting in the typical lens sag value of <60 µm.  At Focuslight, optical components are manufactured on a wafer base with Focuslight’s own wafer-level simultaneous structuring technology, which is applicable to any kind of inorganic optical material. From CaF2 and MgF2 crystals, to high-grade fused silica or high-index glasses, to semiconductor-industry quality Si and Ge material, the wafer-based products cover a wide range of wavelengths from DUV to FIR, structuring optics with nearly unlimited complexity of 1D acylindrical and prismatic surface geometries. Especially (but not exclusively) for silicon, this includes optical and mechanical features for alignment and assembly, opening up the opportunity to implement the products for optomechanical and optoelectronical functionalities. With this processing technology, the lens sag can achieve as large as 4 mm (4000 µm) at an exit angle of 0°~80° on silicon optics, which maximizes the numerical aperture (NA) that a silicon optics could achieve and exceeds the limit of the silicon optics processed with conventional technologies. This enables products that have been hard or impossible to be produced by classical lithographical technologies, such as deep-sag decentered lenses, blazed gratings, chirped arrays or integrated prisms.

As our Product Line Manager of Laser Optics Business Unit Dr. Daniel Braam states: “The possibilities are almost unlimited – we offer a technology that is capable of making unique optical solutions to drive revolutionary applications. Now we have extended this to silicon, creating a new building block for a wide range of next generation silicon photonics, enabling biosensing, PICs, and much more.”

Focuslight wafer-based production technology produces polished wafers up to 300 x 300 mm², making it possible to produce tens of thousands of lenses in a two-step process with a consistently high level of quality. It is a scalable and cost-effective production technology for very high quantities, making the product affordable for massive applications such as IoT, biosensing, smart terminals, etc. The advantages of unique performance and cost structure of this technology have been well demonstrated by Focuslight being a dominant Fast Axis Collimator (FAC) supplier for fiber laser pumping market with over 20 million pieces shipment per year.

Silicon optics typically have low transmission efficiency without AR coating. A precise and optimized design of a proper coating recipe for silicon optics and production process of optical coating can ensure good product performance and long-term operational reliability. Focuslight has in-house capability to design, manufacture and supply high quality coatings for optical communications, instrumentation, and medical applications, as well as conducting thin film analysis and measurement. A wide variety of coatings to cover the wavelength range from the deep ultraviolet (DUV) to infrared (IR) can be customized.