We investigate two different approaches for imprinting orbital angular momentum (OAM) on different spectral components of a broadband ultraviolet beam with wavelength 350-500 nm for application in quantum optical coherence tomography. Two different approaches using a spiral phase plate (SPP) are studied to achieve this goal. The first approach involves using only a SPP, calibrated for a particular wavelength, for broadband application. However, this approach leads to the presence of unmodulated components in the output beam. In the second approach, combination of SPP and grating is used to remove the unmodulated part and to filter out the imprinted OAM beam.
ACKNOWLEDGEMENTS
This work is supported by Villum Fonden (Villum Investigator project Table-Top Synchrotrons, No. 00037822) and Horizon Europe, the European Union’s Framework Programme for Research and Innovation, under Grant Agreement No. 101070062 (SEQUOIA). Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union. The European Union cannot be held responsible for them.
Traditional spontaneous parametric down-conversion (SPDC) generally has a broad spectral band, while quantum optical coherence tomography (QOCT) aims to achieve an ultra-broadband joint spectrum to ensure good axial resolution. Ultra-broadband supercontinuum (SC) sources enable axial resolutions of approximately 1 µm in OCT. This study investigates the impact of ultra-broadband SPDC using an SC source to generate entangled photon pairs within the 700-1000 nm range. By examining the tuning capabilities and dimensional design of the Beta Barium Borate (BBO) crystal, we explore the combination of the OCT SC source and SPDC for QOCT. The findings contribute to future developments in QOCT.
We present an ultrahigh-speed Swept Source Optical Coherence Tomography (SS-OCT) system that allows a volume rate of 400 Hz paired with a Time Domain (TD) subsystem. For the SS-OCT, a 40 MHz swept source is used, while for the TD-OCT, a broadband source. Both systems employ a scanning system that consists of a KTN scanner paired with a galvoscanner. The KTN crystal scans the beam laterally at 100 kHz. This allows B-scan OCT repetition rate, while with the galvoscanner 200 lines are obtained at 400 Hz in the en-face display of both SS-OCT and TD-OCT systems.
In this report, a novel calibration method is introduced, which can be used in camera-based Optical Coherence Tomography (OCT) instruments employing several spectrometers. To ensure that all spectrometers are calibrated, i.e. they sense the same spectral range and the distribution of the optical frequencies across the pixels of the cameras is the same, a hybrid method was used involving (i) a hardware procedure for an initial estimation of the edges of the spectra and (ii) a numerical Monte-Carlo based technique. The utility of such a procedure is demonstrated in an OCT system using a Balance-Detection (BD) scheme. The OCT system employs a single transmission diffraction grating and is driven by a supercontinuum source operating in the visible spectral range. Spectral alignment is paramount in producing high-sensitivity images free of artefacts. To ensure correct calibration, and speed up the calibration procedure, the Master-Slave (MS) technique of generating axial reflectivity profiles is employed. Preliminary results show an improvement of the signal of ~ 3dB and a mitigation of the background noise of over 5 dB.
UV supercontinuum based on gas filled anti resonant hollow core fibers is demonstrated to have passed a major milestone by providing spectral properties comparable to those of plasma arc lamps, namely a broad, flat, low noise, and stable spectrum. The primary advancement is the use of pump modulation which flattens the spectrum by more than 20dB. As proof of concept, results from scatterometry measurements, with both UV supercontinuum and plasma arc lamps are shown to produce comparable results. However, UV supercontinuum can meet additional requirements making it suitable for many cutting-edge UV metrology applications such as imaging and spectroscopy.
We present an ultrafast swept source for optical coherence tomography (OCT) at a central wavelength of 1050 nm with a 86 nm bandwidth. Based on low noise supercontinuum dynamics and time stretch, this akinetic swept source operates at 10 MHz. The fast sweep rate and the low noise of the source enable high-speed imaging at a wavelength suitable for biological tissue (eye, skin). Such a light source presents a significant potential in achieving a large bandwidth beyond the limitations of current high-speed swept-source technologies.
Fiber-based supercontinuum (SC) generation has been a subject of intense interest over the last decade, with a significant impact on both basic science and industry. New uses for SC fiber sources are constantly emerging due to their unique properties that combine high brightness, visible to mid-infrared (MIR) wavelength coverage, fiber delivery, and single-mode output. Recent years have seen significant progress in overcoming the current shortcomings of SC sources in terms of wavelength coverage towards the 2 to 20 mu molecular fingerprint mid-infrared (MIR) region and in the ultraviolet (UV) down to 100 nm, while also improving stability, noise, coherence, power density, and robustness. In this talk, we will review all the recent advances in supercontinuum generation in a range of specialty optical fibers including: fluoride, chalcogenide, telluride, and silicon-core fibers for the MIR; UV-grade silica fibers and gas-filled hollow-core fibers for the UV range; and all-normal dispersion fibers for ultra-low noise coherent SC generation. Significant developments have been made in reaching target UV and MIR wavelength ranges, and the fiber SC has matured considerably to become a truly disruptive technology able to meet a range of societal and industrial challenges.
We present an akinetic swept-source based on all-normal-dispersion supercontinuum generation using a low-noise femtosecond laser. Its 80-MHz repetition-rate and 55-nm bandwidth centered at 1060-nm are suitable for fast optical coherence tomography.
As the world's leading manufacturer of supercontinuum sources over the last 15 years, NKT Photonics will present the applications that have driven the supercontinuum technology forward: From the earliest introduction in commercial microscopes to the most recent industrial applications in highly demanding industries like semiconductor metrology. Over the years, the supercontinuum technology has made the development of several state-of-the-art applications possible, e.g. confocal microscopy, FLIM, STED, OCT, etc.. The supercontinuum technology started in research lab applications but is now mature and reliable and can be used in a wide variety of industrial process monitoring applications.
We report a high pulse, all-fiber supercontinuum source generated by pumping 2 ns long pulses at 100kHz from an ytterbium-doped fiber amplifier (YDFA) into a 15 m tapered photonics crystal fiber (PCF). The YDFA operates at 1066 nm, and the zero-dispersion wavelength of the PCF is at 1040 nm. The PCF is a 15 µm core at the input, tapered down to 5 µm at the output. The tapering is done such that the core-pitch ratio is maintained along the length of the fiber used. The resulting supercontinuum spans from 450 nm to 2400 nm, with a total pulse energy of more than 7uJ. The supercontinuum covers the visible spectrum making it useful for applications that require substantial pulse energies such as photoacoustic tomography.
Supercontinuum (SC) lasers are of high interest for applications like multispectral photoacoustic imaging (MSPAI), where the wide optical bandwidth of the SC laser system facilitates functional investigations on top of the structural information of various endogenous agents inside the human body. The current work addresses a promising attempt at devising high pulse energy SC laser source using telecom-range diode laser systems and few meters of standard single-mode fibers for various MSPAI applications in near-infrared (NIR) and extended-NIR wavelength regions.
An all-fiberized tunable repetition rate (50kHz-10MHz) SC source for photoacoustic microscopy (PAM) and optical coherence tomography (OCT) is developed. OCT is a scattering based imaging technique, requiring low spectral noise. Noise level requirement in OCT is usually mitigated using high repetition rate (MHz) laser sources. On the other hand, PAM is a hybrid imaging modality based on optical absorption that requires high pulse energies, thus, sources operating at lower repetition rates (kHz) are preferred. Nevertheless, it is always important to quantify and understand the RIN dynamics of the SC sources for good quality PAM and OCT images.
We demonstrate a 70 mol % GeO2 doped fiber for mid-infrared supercontinuum generation. Experiments ensure a highest output power for a broadest spectrum from 1000nm to 3000nm from this fiber, while being pumped by a broadband 4 stage Erbium fiber based MOPA. Our investigations reveal the unexploited potential of Germania doped fiber for mid-infrared supercontinuum generation. To the best of our knowledge, this is the record power, for an ultrabroadband, all-fiberized, and compact device size supercontinuum light source based on Silica and Germania fiber, ever demonstrated to the date.
In this work, we report a cost-effective supercontinuum (SC) laser-based multispectral photoacoustic spectroscopy (MSPAS) system for studying spectral characteristics of various analytes. We demonstrate an in vitro label-free monitoring of the analytes in the extended near-infrared (NIR) (1540–1840 nm) spectral range. We further demonstrate how a simple ratiometric analysis in conjunction with linear regression can be used for accurate prediction of glucose over commonly encountered physiological levels inside the human body (0–400 mg/dL). Looking forward, the proposed SC-based MSPAS system provides a framework for the development of label-free and non-invasive monitoring multiple bio-analytes accurately, with potential translation to clinical in vivo applications.
Mid-IR supercontinuum sources are a new type of source for the 2-4.5 μm spectrum, but their weight, size and power consumption has previously made them unsuitable for mobile sensing. We demonstrate a highly compact supercontinuum source with a weight of <1 kg and a power consumption of <15 W emitting a spectral brightness comparable to that of a synchrotron and covering the entire 1.8-4.4 μm spectrum. We will also discuss challenges and opportunities of working with a broadband source instead of a single line or tunable source and touch upon the future potential for supercontinuum reaching further into the mid-IR
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