We present work towards a visible wavelength tuneable external cavity laser (ECL) on a silicon nitride platform working around 640 nm. A ring resonator Vernier structure on the photonic integrated circuit (PIC) provides delayed feedback with spectral filtering and tuning. Gain is provided by a reflective semiconductor optical amplifier (SOA) grown on a GaAs substrate and integrated by pick-and-place flip-chip assembly. In a novel coupling scheme, the 1-dB in-plane placement tolerance is relaxed by a multi-mode edge-coupler to ± 2.6 µm in the direction parallel to the SOA edge and to displacements up to 3.5 µm from the PIC interface along the SOA’s optical axis. Pedestals defined in the PIC guarantee vertical alignment.
We employ thickness gauging with a fast terahertz time-domain spectroscopy (TDS) system based on electronically controlled optical sampling (ECOPS) and compare the results with those of a benchmark conventional terahertz TDS system and a mechanical micrometer gauge. The results of all technologies are in good agreement. We show that the ECOPS system is suitable for fast inline thickness measurements, owing to high measurement rate of 1600 traces per second. Moreover, we characterize the system with respect to signal quality. The time-domain dynamic range is ~60 dB for a single-shot measurement, and ~90 dB with 1000 trace averages, which are completed within less than a second (i.e., 0.625 seconds). The time-domain signal-to-noise ratio amounts to ~50 dB and ~80 dB for 1 and 1000 averages, respectively.
This work reports on a compact and robust single-frequency laser emitting at 633 nm, for industrial metrology applications. The system integrates a miniaturized optical isolator, a single-mode fiber coupling and a vapor cell as frequency reference. The achieved absolute frequency stability is 10-8, while the output power from the fiber is >1 mW. The system shows stable operation over an ambient temperature range between 0 and 70°C, with an electrical power consumption of <3 W. This compact laser system can replace gas lasers in industrial metrology applications, and can serve as key component in future quantum-technology devices.
We will present our latest innovations about ultrafast fiber lasers and show how multiphoton microscopy can benefit from these developments. Wavelengths around 900 nm and pulse durations as short as 100 fs remain a challenge for fiber lasers. Here we present a two-color femtosecond fiber laser system with synchronous outputs. One arm emits pulses at a central wavelength of 780 nm and the novel second laser arm is continuously tunable in its central wavelength between 810 nm and 950 nm. This allows the independent excitation of NADH and FAD and therefore enables optical metabolism and oxygen imaging of cells via FLIM and PLIM measurements.
We describe a metabolic-imaging system based on simultaneous recording of lifetime images of NAD(P)H and FAD. The system uses two-photon excitation by a dual-wavelength femtosecond fibre laser. The two wavelengths of the laser, 780 nm and 880 nm, are multiplexed synchronously with the frames or the lines of the scan. The recording system uses two parallel TCSPC FLIM channels, detecting from 420 to 475 nm and 480 to 600 nm. By using the multiplexing functions of the TCSPC modules, separate images for NAD(P)H and FAD are recorded. A third image is obtained for the SHG of the 880 nm laser wavelength. Data analysis delivers images of the amplitude-weighted lifetime, tm, the component lifetimes, t1 and t2, the amplitudes of the components, a1 and a2, the amplitude ratio, a1/a2, and the fluorescence-lifetime redox ratio (FLIRR), a2nadh/a1fad. We demonstrate the performance of the system for metabolic imaging of mammalian skin.
We present an overview of current opto-electronic terahertz platforms designed for industrial applications. We discuss current and future market perspectives with respect to competing technologies and killer applications. “Make-or-break” features for industrial use are cost and volume reduction alongside with increased robustness and measurement speed. These market challenges are discussed for different technologies, and one representative industrial application is shown for each technology.
We are reporting on a Multi-Color Laser Engine (MLE) multiplexing four wavelengths (405 nm, 488 nm, 561 nm, 640 nm) by means of a Photonic Integrated Circuit (PIC) with Silicon Nitride (SiN) waveguides. Multiple building blocks are tested that allow manipulating the light in the waveguides to achieve fiber switching and variable optical attenuation. To slow down facet degradation and extend chip lifetime at near Ultra-Violet (UV) wavelengths (405 nm), a lateral endcap is implemented on chip and tested for reliability. Reasonable coupling and on-chip losses have been achieved in view of a practical use of the technology.
Compact and robust external-cavity diode laser (ECDL) systems are a mandatory requirement for many next-generation quantum technology applications, e.g. quantum communication and quantum sensors. Today’s commercially available ECDLs are used for proof-of-principle demonstrations of such applications, however do not meet the requirements for the use in real-world environments. We investigate a novel design for a compact and robust ECDL suitable for the integration into first quantum technology applications. Experimental results of first prototypes are presented and compared to a commercially available ECDL and numerical simulations.
We introduce a novel industrial grade 193nm continuous-wave laser light source for proximity mask-aligner lithography. A diode seed laser in master-oscillator power-amplification configuration is frequency-quadrupled using lithiumtriborate and potassium-uoro-beryllo-borate non-linear crystals. The large coherence-length of this monomodal laser is controlled by static and rotating shaped random diffusers. Beam shaping with imaging and non-imaging homogenizers realized with diffractive and refractive micro-optical elements is compared in simulation and measurement. We demonstrate resolution patterns offering resolutions <2 µm printed with proximity gaps of 20 µm.
We present and discuss Talbot mask-aligner lithography, relying on a continuous wave laser emitting at 193nm for the illumination. In this source, a diode laser at 772nm is amplified by a tapered amplifier in master-oscillator power-amplifier configuration and frequency-quadrupled in two subsequent enhancement cavities using lithium triborate and potassium fluoro-beryllo-borate nonlinear crystals to generate the emission at 193 nm. The high coherence and brilliance of such an illumination source is predestined for plane wave mask-aligner illumination, crucial in particular for high-resolution lithographic techniques such as Talbot lithography and phase-shift masks. Talbot lithography takes advantage of the diffraction effect to image periodic mask features via self-replication in multiples of the Talbot distance behind the photomask when exposed by a plane wave. By placing a photoresistcoated wafer in one of the Talbot planes, the mask pattern is replicated in the resist. Periodic patterns with diverse shapes are required for wire grid polarizers, diffraction gratings, and hole arrays in photonic applications as well as for filters and membranes. Using an amplitude mask with periodic structures, we demonstrate here with such a technique sub-micron feature sizes for various designs at a proximity gap of 20 µm.
For several fields such as spectroscopy, metrology, and lithography, laser sources in the ultraviolet (UV @ 386 nm) or deep ultraviolet (DUV @ 193 nm) spectral range rely on broad band or pulsed laser systems such as excimer lasers. Highly brilliant semiconductor laser systems could advance these fields further as they are more reliable and easier to handle.
One way to achieve the UV emission is using a 772 nm emitting semiconductor master oscillator - power amplifier (MOPA) laser system whose emission is frequency doubled once or twice in a later step. The laser system will be built into a small and compact package and consists of a MO, which is a distributed feedback (DFB) ridge waveguide (RW) laser. The diffraction limited laser emission with a single spectral mode is coupled into the PA for the amplification of the output power up to 3 W. The PA is a semiconductor laser with a RW and a tapered section. Optical feedback can be minimized by using a micro-optical isolator, which is placed between MO and PA that allows a linewidth of < 3 MHz.
We will present further experimental results of the MOPA system in detail. This includes the emission characteristics, the spectral emission behavior, and the robust setup by applying several thermal cycles and shaking tests.
On the base of the same laser system, wavelengths of 780 nm or 785 nm could facilitate small rubidium atomic clocks or Raman spectroscopy respectively. Especially when using distributed Bragg reflector laser diodes an even smaller linewidth can be achieved.
This work reports on a compact diode-laser module emitting at 633 nm. The emission frequency can be tuned with temperature and current, while optical feedback of an internal DBR grating ensures single-mode operation. The laser diode is integrated into a micro-fabricated package, which includes optics for beam shaping, a miniaturized optical isolator, and a vapor cell as frequency reference. The achieved absolute frequency stability is below 10−8 , while the output power can be more than 10 mW. This compact absolute frequency-stabilized laser system can replace gas lasers and may be integrated in future quantum technology devices.
Several holographic and interferometric applications would benefit significantly from a diode laser based coherent light source near 633 nm. For this purpose a miniaturized master-oscillator power-amplifier (MOPA) was developed. The MOPA is integrated in a sealed package together with a custom-built CdMnTe-based micro-optical isolator to shield the MO from optical feedback. The MOPA reaches an optical output power of up to 30 mW near 633 nm. Its single-mode emission is tunable over 0.5 nm by temperature and 1.0 nm by a grating heater. The package offers the integration of a gas cell and a polarization maintaining fiber port.
We present a novel compact laser device based on a semiconductor master-oscillator power-amplifier (MOPA) emitting at 772 nm, suitable for quantum optic and spectroscopy. The optical performance of the laser device is characterized. For miniaturized lasers the thermal management is challenging, we therefore perform thermal simulations and measurements.
The first demonstrator is emitting more than 3 W optical power with a linewidth below 2lMHz. Using this MOPA design also compact devices for quantum optics (e.g. rubidium atomic clock) and seed lasers for frequency conversion can be realized [1].
We present a novel industrial-grade prototype version of a continuous-wave 193 nm laser system entirely based on solid state pump laser technology. Deep-ultraviolet emission is realized by frequency-quadrupling an amplified diode laser and up to 20 mW of optical power were generated using the nonlinear crystal KBBF. We demonstrate the lifetime of the laser system for different output power levels and environmental conditions. The high stability of our setup was proven in > 500 h measurements on a single spot, a crystal shifter multiplies the lifetime to match industrial requirements. This laser improves the relative intensity noise, brilliance, wall-plug efficiency and maintenance cost significantly. We discuss first lithographic experiments making use of this improvement in photon efficiency.
Photonic Integrated Circuits (PIC) will change the fundamental paradigms for the design of multi-color laser engines for life sciences. Exemplified with flow cytometry (FCM), integrated optical technology for visible wavelengths will be shown to open a new spectrum of possibilities to control flow cell illumination patterns, such as the number of output spots, the spot size, and even complex patterns generated by interferometry. Integration of additional optical functions such as variable optical attenuation, wavelength division multiplexing or fast shutters adds value to the PIC. TOPTICA is demonstrating integration of PICs in present Multi-color Laser Engine (MLE) architectures. Multiple wavelengths (405nm, 488nm, 561nm, 640nm) are coupled free space into the chip, leveraging its beam steering COOLAC (Constant Optical Output Level Auto Calibration) technology for automatic realignment, thus overcoming the need of fiber input delivery. Once in the waveguide, the light can be redirected and shaped to a desired output pattern and pitch, reducing the need of discrete optical components. In this work, we will discuss the implementation of various building blocks in PIC technology for MLEs and analyze the advantages over current macroscopic counterparts.
This work reports on a compact single-mode diode laser emitting at 633 nm based on an AlGaAs/AlGaInP structure with an integrated DBR surface grating. The micro-fabricated diode laser package includes optics for beam shaping, optical isolation and single-mode fiber coupling. The miniaturized optical isolator is based on cadmium manganese telluride, which provides a large Verdet constant and thus enables the realization of a compact Faraday rotator in the visible spectral range. We discuss the performance and the technological challenges for this approach. Furthermore, we present prospects towards the integration of atomic reference cells into compact laser systems. This would enable the realization of absolute frequency-stabilized diode lasers that could be used in quantum technology devices.
Several holographic and interferometric applications would benefit significantly from a diode laser based coherent light source near 633 nm. For this purpose a laser diode based on an AlGaAs/AlGaInP structure for emission in the red spectral range was developed. The laser chip features a ridge waveguide and a DBR surface grating at the rear side with a peak reflectivity at 633 nm. The laser was mounted in a butterfly-style package for temperature stabilization. The beam emitted by the laser diode was shaped with two cylindrical micro-lenses and passed through a custom-built CdMnTebased micro-optical isolator. The beam behind the isolator was coupled into a polarization maintaining (PM) single-mode fiber using an aspherical lens. The optical output power of the fiber was about 1.7 mW at 100 mA.
The performance of large ground-based optical telescopes is limited due to wavefront distortions induced by atmospheric turbulence. Adaptive optics systems using natural guide stars with sufficient brightness provide a practical way for correcting the wavefront errors by means of deformable mirrors. Unfortunately, the sky coverage of bright stars is poor and therefore the concept of laser guide stars was invented, creating an artificial star by exciting resonance fluorescence from the mesospheric sodium layer about 90 km above the earth’s surface. Until now, mainly dye lasers or sumfrequency mixing of solid state lasers were used to generate laser guide stars. However, these kinds of lasers require a stationary laser clean room for operation and are extremely demanding in maintenance. Under a development contract with the European Southern Observatory (ESO) and W. M. Keck Observatory (WMKO), TOPTICA Photonics AG and its partner MPB Communications have finalized the development of a next-generation sodium guide star laser system which is available now as a commercial off-the-shelf product. The laser is based on a narrow-band diode laser, Raman fiber amplifier (RFA) technology and resonant second-harmonic generation (SHG), thus highly reliable and simple to operate and maintain. It emits > 22 W of narrow-linewidth (≈ 5 MHz) continuous-wave radiation at sodium resonance and includes a re-pumping scheme for boosting sodium return flux. Due to the SHG resonator acting as spatial mode filter and polarizer, the output is diffraction-limited with RMS wavefront error < λ/25. Apart from this unique optical design, a major effort has been dedicated to integrating all optical components into a ruggedized system, providing a maximum of convenience and reliability for telescope operators. The new remote-pumping architecture allows for a large spatial separation between the main part of the laser and the compact laser head. Together with a cooling-water flow of less than 5 l/min and an overall power consumption of < 700 W, the system offers a maximum of flexibility with minimal infrastructure demands on site. Each system is built in a modular way, based on the concept of line-replaceable units (LRU). A comprehensive system software, as well as an intuitive service GUI, allow for remote control and error tracking down to at least the LRU level. In case of a failure, any LRU can be easily replaced. With these fiber-based guide star lasers, TOPTICA for the first time offers a fully engineered, off-the-shelf guide star laser system for groundbased optical telescopes providing convenient, turn-key operation in remote and harsh locations. Reliability and flexibility will be beneficial in particular for advanced satellite and space debris tracking as well as LIDAR applications.
Large telescopes equipped with adaptive optics require high power 589-nm continuous-wave sources with emission linewidths of ~5 MHz. These guide-star lasers should be highly reliable and simple to operate and maintain for many years at the top of a mountain facility. After delivery of the first 20-W systems to our lead customer ESO, TOPTICA and MPBC have begun series production of next-generation sodium guide-star lasers. The chosen approach is based on ESO’s patented narrow-band Raman fiber amplifier (RFA) technology [1]. A master oscillator signal from a TOPTICA 50-mW, 1178-nm diode laser, with stabilized emission frequency and linewidth of ~ 1 MHz, is amplified in an MPBC polarization-maintaining (PM) RFA pumped by a high-power 1120-nm PM fiber laser. With efficient stimulated Brillouin scattering suppression, an unprecedented 40 W of narrow-band RFA output has been obtained. This is spatially mode-matched into a patented resonant-cavity frequency doubler providing also the repumper light [2]. With a diffraction-limited output beam and doubling efficiencies < 80%, all ESO design goals have been easily fulfilled. Together with a wall-plug efficiency of < 3%, including all system controls, and a cooling liquid flow of only 5 l/min, the modular, turn-key, maintenance-free and compact system design allows a direct integration with a launch telescope. With these fiber-based guide star lasers, TOPTICA for the first time offers a fully engineered, off-the-shelf guide star laser system for ground-based optical telescopes. Here we present a comparison of test results of the first batch of laser systems, demonstrating the reproducibility of excellent optical characteristics.
We report on the realization of a narrow-band continuous-wave laser source in the deep-ultraviolet. Via two consecutive second-harmonic processes starting from a near-infrared diode laser system, we demonstrate an output power of more than 15 mW at 193 nm. The setup is capable of mode hop-free frequency tuning over a range of 100 GHz und coarse tuning over more than 5 nm. We see direct applications of this laser source in the fields of semiconductor metrology and high-resolution spectroscopy in the deep-ultraviolet.
A continuous-wave deep-ultraviolet light source is demonstrated based on a grating-stabilized diode laser pump system and two consecutive nonlinear conversion stages. Using the crystal Potassium Fluoroberylloborate (KBBF), direct second-harmonic generation to 191 nm could be realized with an output power of up to 1.3 mW. The linewidth at this wavelength is estimated to be around 100 kHz. The emission can be tuned mode hop-free over 40 GHz. Our scheme can be easily extended to 193 nm or – given the availability of suitable fundamental sources – to wavelengths as small as 165 nm. These parameters make our light source an ideal tool for applications in deep-ultraviolet metrology and photoemission spectroscopy.
The frequency-doubled radiation of an Erbium-doped fiber laser is used for supercontinuum generation in a small-core
microstructured fiber with two zero-dispersion wavelengths. Average powers up to 49 mW are launched
into the highly nonlinear photonic-crystal fiber. The generated supercontinuum shows a short-wavelength peak
centered around 670 nm and a long-wavelength peak centered around 1100 nm. More than 35 mW is contained
in the short-wavelength peak. We use the anomalous dispersion of a SF10 prism compressor to compress the
short-wavelength peak of the spectrum. The compressed pulse has a central wavelength of 670 nm and a duration
of 27 fs.
The different flavors of today's and future multilayer transmission networks are analyzed highlighting the main infrastructure, capital expenditure (CAPEX) and operational expenditure (OPEX) contributions to total cost of ownership (TCO). Depending on different carrier requirements, critical parameters and general design rules for optimum overall cost positions are discussed. To illustrate and evaluate the impact of given boundary conditions, some case studies will be presented where new technologies lead to significant OPEX/CAPEX savings.
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