Manufacturing and measurement of freeform optics

High-power broad-area diode lasers are the most efficient light sources, with 90-μm stripe GaAs-based 940-980 nm single emitters delivering > 10 W optical output at a power conversion efficiency ηE(10 W) > 65%. A review of efforts to increase ηE is presented here and we show that for well-optimized structures, the residual losses are dominated by the p -side waveguide and nonideal internal quantum efficiency ηi . The challenge in measuring efficiency to sufficient precision is also discussed. We show that ηE can most directly be improved using low heat sink temperature THS with ηE(10 W) reaching > 70% at THS = -50 °C. In contrast, increases in ηE at THS = 25 °C require improvements in both material quality and design, with growth studies targeting increased ηi and reduced threshold current and design studies seeking to mitigate the impact of the p-side waveguide. “Extreme, double asymmetric” (EDAS) designs are shown to substantially reduce p-side losses, at the penalty of increased threshold current. The benefit of EDAS designs is shown here using diode lasers with 30-μm stripes, (in development as high beam quality sources for material processing). Efficiency increases of ~ 10% relative to conventional designs are demonstrated at high powers.

Efficient High-Power Laser Diodes

Two different approaches for ultra flat image acquisition sensors on the basis of artificial compound eyes are examined. In apposition optics the image reconstruction is based on moire- or static sampling while the superposition eye approach produces an overall image. Both types of sensors are compared with respect to theoretical limitations of resolution, sensitivity and system thickness. Explicit design rules are given. A paraxial 3×3 matrix formalism is used to describe the arrangement of three microlens arrays with different pitches to find first order parameters of artificial superposition eyes. The model is validated by analysis of the system with raytracing software. Measurements of focal length of anamorphic reflow lenses, which are key components of the superposition approach, under oblique incidence are performed. For the second approach, the artificial apposition eye, a first demonstrator system is presented. The monolithic device consists of a UV-replicated reflow microlens array on a thin silica-substrate with a pinhole array in a metal layer on the backside. The pitch of the pinholes differs from the lens array pitch to enable an individual viewing angle for each channel. Imaged test patterns are presented and measurements of the angular sensitivity function are compared to calculations using commercial raytracing software.

/pdf/artificial-compound-eyes-different-concepts-and-their-2jurf33yvb.pdf

Artificial compound eyes: different concepts and their application for ultraflat image acquisition sensors

The visual revolution triggered by the commercial application of digital image capturing devices generates the need for new miniaturized and cheap optical imaging systems and cameras. However, in imaging we can observe only a permanent miniaturization of elements but always similar optical principles are applied which are known to the optical designers for many decades. With the newly gained spectrum of technological capabilities it is the time to ask: Which vision principle should be used at which level of miniaturization and which technology has to be applied in order to achieve the perfectly adapted imaging system? In this paper we present an overview of two insect inspired artificial compound eye concepts for compact vision systems fabricated by lithographic technologies, one classical miniaturized objective and its wafer-scale fabrication and the use of variable focal length liquid lenses for miniaturized autofocus- and zoom objectives without moving parts.

Novel optics/micro-optics for miniature imaging systems

Efficient homogeneous illumination of rectangular or circular areas with LEDs is a promising application for doublesided microlens arrays. Such illumination schemes employ a primary optics - which can be realized with a concentrator or a collimation lens - and a secondary optics with one or more double-sided microlens arrays and a collection optics for superposing the light from the individual array channels. The main advantage of this design is the achievable short system length compared to integrating lightpipe designs with subsequent relay optics. We describe design rules for the secondary optics derived from simple ABCD-matrix formalism. Based on these rules, sequential raytracing is used for the actual optics system design. Double-sided arrays are manufactured by polymer-on-glass replication of reflow lenses. With cylindrical lens arrays we assembled high-brightness RGB-illumination systems for rectangular areas. Hexagonal packed double-sided arrays of spherical lenslets were applied for a miniaturized circular spotlight. Black matrix polymer apertures attached to the lens array helped to avoid unwanted straylight.

Homogeneous LED-illumination using microlens arrays

The potential and limits of micromoulding technology for the wafer scale hybrid integration of micro-optic elements on top of arbitrary substrates like glass, Silicon, III/V-semiconductors by a process which is performed in a modified contact mask aligner. The elements are characterised by high precision and stability, temperature stable and precise pitch, index, homogeneity, uniformity across the wafer, and they fulfill additional requirements for a practical application (AR-coating, separation in a dicing saw). Additionally, the technology for a two- sided replication of elements has been developed. The precision of lens arrays fabricated by reflow and UV-moulding is investigated, and the high performance of these arrays in the collimation of fiber arrays is shown. Steps toward a wafer scale integration of lens arrays with vertical cavity surface emitting lasers (VCSELs) by locally selective replication are demonstrated.

Polymer UV-molding for micro-optical systems and O/E-integration

Driven by the potential of the fiber laser market, the development of high brightness pump sources has been pushed
during the last years. The main approaches to reach the targets of this market had been the direct coupling of single
emitters (SE) on the one hand and the beam shaping of bars and stacks on the other hand, which often causes higher cost
per watt. Meanwhile the power of single emitters with 100μm emitter size for direct coupling increased dramatically,
which also pushed a new generation of wide stripe emitters or multi emitters (ME) of up to 1000μm emitter size
respectively "minibars" with apertures of 3 to 5mm. The advantage of this emitter type compared to traditional bars is
it's scalability to power levels of 40W to 60W combined with a small aperture which gives advantages when coupling
into a fiber.
We show concepts using this multiple single emitters for fiber coupled systems of 25W up to 40W out of a 100μm fiber
NA 0.22 with a reasonable optical efficiency. Taking into account a further efficiency optimization and an increase in
power of these devices in the near future, the EUR/W ratio pushed by the fiber laser manufacturer will further decrease.
Results will be shown as well for higher power pump sources. Additional state of the art tapered fiber bundles for
photonic crystal fibers are used to combine 7 (19) pump sources to output powers of 100W (370W) out of a 130μm
(250μm) fiber NA 0.6 with nominal 20W per port. Improving those TFB's in the near future and utilizing 40W per pump
leg, an output power of even 750W out of 250μm fiber NA 0.6 will be possible. Combined Counter- and Co-Propagated
pumping of the fiber will then lead to the first 1kW fiber laser oscillator.

High brightness fiber laser pump sources based on single emitters and multiple single emitters

Lasers for marking, direct application laser systems as well as high power solid state lasers require highly reliable, high
efficient and low cost laser diodes. Especially fiber lasers and direct diode systems have additionally the need for high
brightness. For a very long time either single emitter solutions with low brightness and costs or beam shaped bar
solutions with high brightness and high costs served those needs. Since roughly 2 years multiple single emitter solution
are more and more penetrating the market showing a high potential for serving all needs of a broad customer base.
Based on the 50W product introduced by the middle of 2009 we would like to show the design which is based on
qualified and highly stable single emitters.

Roadmap to low cost, high brightness diode laser power out of the fiber

A hybrid interface of solid state single-photon sources and atomic quantum memories is a long sought-after goal in photonic quantum technologies. Here we demonstrate deterministic storage and retrieval of photons from a semiconductor quantum dot in an atomic ensemble quantum memory at telecommunications wavelengths. We store single photons from an InAs quantum dot in a high-bandwidth rubidium vapour based quantum memory, with a total internal memory efficiency of $(12.9 \pm 0.4) \%$. The signal-to-noise ratio of the retrieved photons is $18.2\pm 0.6$, limited only by detector dark counts. This demonstration paves the way to quantum technologies that rely on distributed entanglement, and is especially suited for photonic quantum networks.

pdf/deterministic-storage-and-retrieval-of-telecom-quantum-dot-9x7ho4m9.pdf

Deterministic Storage and Retrieval of Telecom Quantum Dot Photons Interfaced with an Atomic Quantum Memory

Structural and functional analysis of a new co-processed tableting excipient for food compaction processes

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Lars Wagner

Author Tools

Chat about Author