Researchers around the world focus on the search for the perfect quantum system suitable for applications of ‘quantum technology 2.0’. Those range from quantum sensing, via communication to computing using qubits. Even though these applications are based on quantum effects, their diversity brings with them a variety of different requirements on the ideal quantum systems. A prominent class of quantum systems are defect centers in solid-state materials. They have been found to represent quantum systems that are precisely measurable and controllable, while being almost unaffected by their environment. Characterization of the different systems at various ambient conditions using photoluminescence excitation (PLE) spectroscopy techniques helps identifying the right quantum system for the respective target application. In this context we discuss the design and unique performance characteristics of widely tunable CW optical parametric oscillators as novel laser light sources for PLE.
Holographic optical elements (HOEs) are versatile alternatives and complements to conventional refractive and reflective optics. With few exceptions, the manufacturing of HOEs based on holographic recording requires monochromatic light with a long coherence length and narrow linewidth, typically provided by lasers operating at a single longitudinal mode. The wavelength of the recording light is a key process parameter as it directly affects the spectral behavior and selectivity of the HOE at replay. Widely tunable continuous-wave optical-parametric-oscillator (OPO) devices are becoming increasingly popular in the field of applied holography, offering unparalleled wavelength coverage in the visible and near infrared spectral range in a single device with coherence and stability properties that match holography’s stringent requirements. The OPO’s wide tuning range translates into equally wide ranges of HOE replay wavelengths with little to no adjustment of the holographic recording geometry. This allows for drastic simplification of recording tools, as well straightforward adjustment of exposure recipes to compensate for any postprocessing shifts.
In this paper, we present newly developed cw OPO systems operating at Watt-level output powers and their use in holographic recordings of uniformly slanted volume holographic gratings (VHGs). The tunability of the OPO system’s output wavelength is a crucial feature enabling the use of highly efficient scanned-beam exposure approaches. We demonstrate this by using a single recording geometry to produce an array of slanted VHGs whose notch spectral band centres were defined by adjusting only the recording wavelength supplied by the OPO systems. Importantly, most of those recording wavelengths did not correspond to commonly available laser wavelengths – they were only achievable thanks to the free tunability of the OPO sources. Captured in state-of-the art photopolymer material, the holographic filters themselves exhibit anomalous reflection-like behavior with high diffraction efficiency (DE) giving optical densities up to OD4, and linear angle-tuning around normal incidence. Collectively this array of filters covers the full visible spectrum. The capability presented here is straightforwardly extended to more complex VHGs like HOEs with optical power, wavelength-multiplexed waveguide-couplers and free-space holographic image combiners.
We discuss principles, design challenges, performance highlights as well as current limitations of state-of-the-art widely tunable continuous-wave optical parametric oscillators sought to be practical for implementation as turn-key systems. Employing a flexible two-stage design concept that can be adapted to several single-frequency laser pump sources, we demonstrate how a wavelength range from 450 nm up to 3500 nm can be covered almost seamlessly. Emerging keyapplications in the realm of quantum technology, like fundamental studies of novel color centers in diamond, are presented in an illustrative manner.
Widely tunable continuous wave optical parametric oscillators (cw OPOs) are gaining popularity as novel sources of tunable laser light, not least due to the unprecedented wavelength coverage in the visible and the near infrared spectral range. While the potential and the advantages of tunable cw OPOs are becoming increasingly recognized, in particular within the quantum research community, the experimental requirements are often challenging. In this context, we discuss the characteristics of state-of-the-art tunable cw OPO designs and describe several tuning schemes tailored to meet various experimental needs. In an illustrative fashion, we compare several recently published experimental datasets from photoluminescence excitation experiments, which have been carried out on ensembles as well as on individual quantum emitters under different experimental conditions.
The huge potential of tunable optical parametric oscillators (OPOs) derives from their exceptional wavelength versatility, as they are in principle not limited by the wavelength coverage dictated by the energy levels and transitions in a laser gain medium. However, while the OPO concept has been experimentally demonstrated already more than half a century ago, the progress in development of practicable and reliable turn-key devices that operate in continuous-wave (cw) mode has been stalled by several technical obstacles. This applies particularly for systems that sought to deliver tunable output across the visible spectral range (VIS), where only relatively recent advances have spurred the development of operationally stable benchtop devices. We discuss the principles and design challenges of such technically practicable cw OPOs, focusing on singly resonant OPO cavity designs that are linked with frequency conversion of the primary OPO output into different ranges of the visible spectrum. In this context, suitable choices and combinations of (quasi-phase-matched) nonlinear crystals are examined. We further discuss the overall performance highlights as well as current limitations of state-of-the art tunable cw OPO designs, and present first measurement results from conceptual approaches to shift and/or extend the wavelength coverage in future design layouts that eventually target commercialization. Last no least, after presenting real-world applications in an illustrative manner, we critically discuss how OPO technology, on the long run, can be expected to perform in the competition with alternatives based on common tunable laser designs.
There is recently an increasing interest in holographic techniques and holographic optical elements (HOEs) related to virtual reality and augmented reality applications which demand new laser technologies capable of delivering new wavelengths, higher output powers and in some cases improved control of these parameters. The choice of light sources for optical recording of holograms or production of HOEs for image displays is typically made between fixed RGB wavelengths from individual lasers (457 nm, 473 nm, 491 nm, 515 nm, 532 nm, 561 nm, 640 nm, 660 nm) or tunable laser systems covering broad wavelength ranges with a single source (450 nm – 650 nm, 510 nm – 750 nm) or a combination. Lasers for holographic applications need to have long coherence length (>10 m), excellent wavelength stability and accuracy as well as very good power stability. As new applications for holographic techniques and HOEs often require high volume manufacturing in industrial environments there is additionally a growing demand for laser sources with excellent long-term stability, reliability and long operational lifetimes. We discuss what performance specifications should be considered when looking at using high average power, single frequency (SF) or single longitudinal mode (SLM) lasers to produce holograms and HOEs, as well as describe some of the laser technologies that are capable of delivering these performance specifications.
Bulk and surface absorption in lithium triborate (LBO) and lithium niobate (LiNbO3) are measured using two sensitive measurement techniques, a photoacoustic spectrometer (PAS) and a photothermal common-path interferometer (PCI). As pump light sources, optical parametric oscillators are employed, covering the wavelength ranges 212 − 2500 nm (PAS) and 1460 − 1900 nm and 2460 − 3900 nm (PCI). The spectrometers are used to measure absorption spectra of optical materials across this wide spectral range and to compare the methods in the shared wavelength regime.
Nonlinear optical materials are important to extend the spectral coverage of existing lasers, mainly via frequency
doubling and with optical parametric oscillators. The quality of the materials and components, e.g. in terms of
residual absorption, is pivotal for the performance of the devices. The paper presents high-sensitivity absorption
measurements of nonlinear optical materials. They were performed using a photoacoustic spectrometer which
combines high sensitivity with broad spectral coverage. This allows one not only to quantify the level of residual
absorption but also to assist in the characterization of the materials in terms of optically relevant impurities and
imperfections. The spectrometer covers the wavelength range between 407 and 2600 nm using a pulsed optical
parametric oscillator as excitation source. Pulse energies up to 100 mJ allow one to record absorption spectra
with a sensitivity down to 10 ppm/cm.
The paper presents spectra of lithium niobate and lithium triborate crystals which are important for highpower
nonlinear optical applications. The results are discussed with respect to material impurities and the
suitability of individual samples for frequency conversion.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.