Reduction of Process Steps via MPO 3D Direct Laser Writing Technology
Due to its maskless 3D Direct Laser Writing technology, Multiphoton Optics’ Two-Photo Polymerization (TPP) process enables the generation of refractive and diffractive microoptical elements with arbitrary shapes in an arbitrary arrangement on a large variety of substrates.
This unlimited freedom of design is a unique feature compared to conventional techniques, and it thus provides the solution for novel device architectures in order to cope with the increasing demand of creating miniaturized devices with multiple functions.
There are two scenarios to employ the technology in microlens fabrication. Individual microlenses or microlens arrays can be fabricated using LithoProf3D® directly on photonic chips or on substrates to be implemented in endoscopic devices for in- and outcoupling purposes. These microlenses can be fabricated by our technology with a surface roughness of 2 to 4 nm, way below the critical value of λ/10 (with λ being the operation wavelength of the device). Thus, microlenses or microlens arrays for devices operating in the IR down to the VIS and the UV range can be created. Aside of this, replication masters can be manufactured, providing mass production capabilities of sophisticated optical designs.
Single microoptical devices, arrays, or even combinations of differently shaped microlenses providing specially designed, novel imaging properties can be conveniently fabricated by LithoProf3D®. These lenses or lens arrays are, for example, very useful for imaging and sensor products in all kind of application scenarios, where these sensor and imaging products are employed.
Assembly of Optoelectronic and Silicon Photonics Packaging
The assembly of optoelectronics and silicon photonics packaging require extremely accurate placement of components to ensure low optical loss and highly efficient light coupling. Additionally, beam shaping and light guidance are essential for optimal illumination and relaxed alignment tolerances. MPO has developed a solution to eliminate 70 % of the usually required process steps to manufacture and align optical elements.
Applications examples for optoelectronic and photonics packages are
- Integrated microoptics for EEL collimation in sensors
- Expansion of effective area in high-speed photodiodes for datacom
- Microlens on laser die for beam shaping
- Microlenses on photodiodes
- Microlenses on VCSEL for ToF applications (e.g. LIDAR)
- Apertures on LEDs
Application Example 1: Microlens on Laser Die for Beam Shaping
Customer Use Case: The customer produces components for detectors. Infrared semiconductor (edge emitting) lasers (EEL) are used as light sources in gas detectors. Manufacturers of detectors require circular beam shapes for their devices. The elliptical beam shape originating from the EEL is thus a challenge. The legacy solution for beam shaping is to mount aspherical or cylinder lenses in front of the laser. The drawbacks are bulky packages and time-consuming costly manual labor resulting from active alignment and fixing.
MPO Solution: MPO’s technology enables the printing of lenses directly on the EEL’s facet. This allows further miniaturization of components, speeds up production of the packaged device and lowers overall production costs by up to 80 %.
Miniaturized packages fabricated with MPO’s technology have been constantly running for more 15,000 hours at an optical power density of more than 1 MW/cm2 with no evidence of degradation of the printed optics.
Application Example 2: Microlenses on Photodiodes
Customer Use Case: The customer is a manufacturer of VCSEL solutions and photodiodes (PD) for datacom transceivers (inter-board fiber connections). High-speed PDs with smaller active area present production and assembly challenges that cannot be solved with legacy solutions. One main challenge is achieving optimal alignment of the PD with the light source in the datacom transceiver package.
MPO Solution: LithoProf3D® will directly print microlenses on PDs to enhance the effective area of the high-speed PD. The equipment will be integrated in the customer’s production workflow. This eliminates the need for active fiber-to-PD alignment and enables miniaturization while ensuring compatibility with assembly processes down the value chain.
Application Example 3: Microlenses on VCSEL for ToF Applications
Legacy Process: 3D sensing in smartphones is enabled by Time-of-Flight (ToF) applications. These applications are realized by implementing optical engines consisting of VCSEL arrays and microlens arrays for beam shaping. Due to the divergence of the VCSEL-emitted laser beam, the illumination is blurred at the edges resulting in suboptimal contrast. A perfectly collimated laser beam would result in better sensing specifications.
Additional applications: 3D cameras for AR/VR, in-cabin monitoring in automotive, LIDAR
MPO Solution: TPP technology can be used to print collimating lenses directly on top of individual VCSELs to collimate the corresponding laser beam. Additionally, TPP technology can be used to create master or molds of complex MLA designs for beam shaping with new functionalities.
Application Example 4: Apertures on LEDs
Customer Use Case: Point light sources are designed for applications where a small emission point is required. Applications for such devices are in optical signal processing, optical encoders, safety light curtains and medical equipment. The customer is a supplier of customer specific optical modules. The challenge is in the upscale of masked point source LEDs.
In the legacy process, the aperture is fabricated on a separate glass with a chrome layer and manually placed on top of the LED chip in a tedious and time-consuming manual process. Upscaling to a few thousand pieces while keeping cost per piece low is not possible.
MPO solution: MPO’s solution is to directly fabricate the aperture on the LED chip on a wafer level. The LED can be then picked and placed using established technologies. This eliminates the restrictions in production capacity and enables processing of several 100,000 pcs/year. The advantages of the process are better miniaturization, faster production (10,000 pcs/day with 1 hour of manual work), higher yield (fully automated semiconductor process) and lower cost (decrease of costs to less than 10 % of current price).
Fabrication of Complex Masters for Replication
Mastering of optical nanostructures or microlens arrays is the state-of-the-art solution for volume production with conventional replication technologies (e.g. NIL, injection molding). However, traditional master fabrication technologies cannot render complex designs and thus do not satisfy the increasing demand for novel optical functionalities. MPO can fabricate complex masters for replication thanks to its free-form capability and maskless laser writing exposure method.
Parallelization via replication of master structures provides a basis for increasing throughput and decreasing fabrication costs at the same time. With our key technology, arbitrarily shaped 3D master structures like individual microlenses of the same or of arbitrarily arranged shapes can be generated. Aside of microlenses, structures suitable for nanoimprint lithography jobs can be individually fabricated with the same approach, making use of the technology’s scalability from the 100 nm to the macro regime. These structures are then used to create a replication tool which then is be used to replicate the master structure on different substrates for a large variety of structure dimensions.
Application Example 1: TPP Master Fabrication
Legacy Process: Master or mold templates are used in replication processes (such as nano-imprint lithography, hot embossing or injection molding) for mass manufacturing (e.g. consumer electronics). The fabrication of these master templates can be very time and cost intensive with conventional technologies (e.g. for lens fabrication for smartphones: several months between different prototype series at costs above 100 k€). This affects the time-to-market from design optimization and validation to the final product.
MPO Solution: TPP technology can be used to accelerate the prototyping phase in terms of costs and time. After the design has been validated, the final master can be fabricated with conventional technologies. Additionally, TPP technology can be used to create master or mold designs which cannot be realized with conventional technologies (e.g. special shaped MLAs) thereby enabling novel functionalities.
Application Example 2: Fresnel Lens for AR/VR Applications
Major players from the AR & VR equipment development and manufacturing space are facing several challenges: Currently available AR/VR glasses are heavy and bulky devices with low comfort for the users. Furthermore, the development of high image quality systems (resolution, field of view, contrast…) faces a bottleneck as legacy technologies are either not suitable to produce sophisticated designs (e.g. Fresnel lenses), require stitching that hinders functionality, or are time-consuming and expensive. This means that designs cannot be validated in a reasonable time frame, lengthening time-to-market in this competitive field.
MPO Solution:LithoProf3D® will be the first technology platform (hardware + software) which will allow the fabrication of circular Fresnel lens molds without stitching artifacts, while maintaining high resolution (groove size < 1 µm) and accuracy (feature size < 1 µm). This will enable fast and easy prototyping of sophisticated optics for AR/VR technology, as well as other applications.
Biomedicine and Life sciences require increasing miniaturization of devices for non-invasive in vivo applications such as in endoscopy. Furthermore, mimicking the biological environment is crucial for cell growth.
MPO’s technology can realize complex microstructures with advanced bio-compatible materials as required. Scaffolds and specially shaped surface structures or functions can be additively and subtractively created which are useful in Tissue Engineering applications. Further applications are possible in drug delivery systems or in microfluidics:
- Unique optical designs for endoscopy
- Complex designs for tissue engineering
- Microfilters with deterministic pore size
Application Example 1: Tissue Engineering
Customer Use Case: Scaffolds in 3D mimicking particular geometries are fabricated fast and reliably up to very large scales using Multiphoton Optics’ unique technology and equipment features. For the restoration of diseased or damaged tissue, the growth of cells on 3D porous scaffolds for tissue engineering is a promising approach to generate autologous tissue. Structure type and size can be simply varied to investigate their influence on primary human microvascular endothelial cells.
Application Example 2: Microfilters for Biomedical Applications
Customer Use Case: Our customer is a global provider of technologies and services for therapeutics. Commercially available membrane filters mainly consist of alternating polymer films (Cast Membranes) with statistic microcracks (induced by various methods) or of statistically arranged polymeric fibers (Cellulose). Resulting from the statistic distribution, the pore size of a specific filter is not clearly defined but exhibits a certain range which makes the characterization of a filter difficult.
MPO Solution: With MPO’s micro 3D printing technology and its real 3D capability, the fabrication of a microfilter can be carried out according to a specific design, with controlled pore size and distribution, to meet individual customer requirements.
Application Example 3: Endoscope lenses
Customer Use Case: The market for endoscopy devices is expected to grow to € 40 bn by 2022. Due to their excessive size, conventional solutions are not suited for observations in extremely small body regions such as blood vessels. The use of thin optical fibers is promising but remains challenging as conventional optics for illumination and imaging drastically increase the formfactor of the packaged device.
MPO solution: Thanks to its print-on-device capability and to its ability to fabricate complex structures in a single process step, MPO’s technology enables the fabrication of miniaturized optical elements directly on the tip of a fiber.