1,721,027 research outputs found
Microfabrication of waveguide-based devices for quantum optics
No full textQuantum optics and photonics play a key part of the field of quantum technology. For these technologies to be of practical use, scale must be realised in both complexity and manufacture. To this end new and improved components are required. The development of these new components is the core of this thesis, with a specific focus on the integration of Bragg gratings into silica waveguide devices. The process used to fabricate these structures, small-spot direct UV writing, is detailed and modelled to build a better understanding of the platform. The small-spot direct UV writing technique is applied to the fabrication of fibre Bragg gratings and proven to be a highly capable technique with great flexibility. This new approach to the fabrication of fibre Bragg gratings is shown to be able to, in one process, write in excess of fifty gratings in a single length of fibre. Such grating structures can yield large data sets for detailed statically analysis. This has allowed for thorough characterisation of the writing technique which showed good agreement with the modelling. Using this characterisation, filters for single photon sources are fabricated, achieving suppression in the stop band of over 50 dB. Other high performance grating devices were also fabricated, such as matched pairs of narrowband ultra-long gratings with 3 dB bandwidths of less than 50 pm. Though the silica waveguide platform offers low optical loss any loss critically degrades the performance of quantum systems. This work aimed to reduce the losses in the platform from coupling between optical fibre and direct UV written integrated waveguides. In order to understand the optical modes of both types of waveguides a bespoke, automated, beam profiling system was built. The system was then used to adjust the fabrication parameters of the integrated waveguides such that their modes matched the fibre. The resultant predicted coupling losses achieved were close to 0.1 dB. In order to directly measure the broadband coupling losses accurately a new technique was developed whereby Bragg gratings were written into both the fibre and the integrated waveguide. By comparing the response of the gratings before and after the coupling between waveguides, coupling loss were measured to an accuracy of ∼0.1 dB. Finally, the use Bragg gratings to enhance the efficiency of superconducting single-photon nanowire detectors was investigated. This was done by using the gratings to form of cavities around the detectors. Testing of these cavity structures showed a potential improvement in efficiency of between 5% and 50%.<br/
Enhanced temperature sensitivity of thermally regenerated direct ultraviolet written gratings in germanium doped core fiber
No full textThe use of thermally regenerated gratings for monitoring harsh environments is becoming increasingly attractive due to their thermal resilience and high precision. They are a unique type of Bragg grating created through annealing UV-laser written Fiber Bragg Gratings (FBGs) at high temperatures (above 600°C) and they have been demonstrated to operate at temperatures over 1000 °C in oxygen free environments. In this work we report two new observations. Firstly, a second phase thermal regeneration process at temperatures above 650°C and secondly an enhanced thermal response for these second phase regenerated gratings of over 140%. Uniquely, fabrication of the gratings was made through a small spot Direct Ultraviolet Writing (DUW) process. This utilizes a high precision four-axis stage system and a frequency double argon-ion continuous wave 244 nm laser that is split and recombined at a focus to form a ~7 µm diameter interferometric spot. A series of 46 different FBGs, from 1400 to 1620 nm, were written into a single non-hydrogen loaded double clad germanium doped 4 µm core fiber (Nufern GF4A). Gratings in the series were written with fluences ranging from 0.05 kJ/cm2 up to 90 kJ/cm2.&more..
Fabrication and characterisation of few mode DBR Brillouin-Raman lasers
No full textStimulated Raman scattering (SRS) fiber lasers remain an area of interest as they provide a simple and compact method of creating lasers at wavelengths beyond the rare-earth ion bands. The authors and others have demonstrated that short π-phase shifted distributed-feedback (DFB) cavity structures can be used to create single-frequency lasers [1–3]. To reach longer wavelengths, cascading SRS cavities are typically used, which usually involve many-meter-long distributed Bragg reflector (DBR) Fabry–Pérot cavities with 100s or 1000s of longitudinal modes. However, to keep the laser system compact, these cavities must be as short as possible, which results in few longitudinal modes and a different behaviour. Siekiera et al. have reported such short DBRs which consist of two 50 mm gratings separated by 120 mm in a high germania fiber with an effective area of 7.3 μm2 [4]. This produced a laser with a threshold of 4 W with a maximum output of 700 mW for 8 W of pump with the expected 607 MHz beat frequency between the few longitudinal modes and 20 dB side mode suppression.Our DBRs were fabricated in the same manner as the previous π-phase shifted DFB laser using UHNA3 fiber again for its high germania content and small effective area of 5.4 μm2 [3]. The DBR’s 241 mm long cavity is formed from two 22 mm gratings at 1116 nm which are 99.9 % reflective. The cavity is pumped with a freespace linearly polarised 1064.4 nm pump setup as shown in Fig. 1a. Unlike Siekiera et al., the lack of an output coupler grating leads to a much higher finesse cavity which, along with the smaller effective area, leads to a lower threshold of 2.2 W, higher maximum output powers of 900 mW at 5 W pump power, and the presence of stimulated Brillouin scattering (SBS) as we saw in our DFB laser, as shown in Fig. 1b. We also see a much reduced broadening with a FWHM of 23 pm for the SRS and 18 pm for the SBS with 70 dB sidemode suppression. Given the similarities to our DFB we expected a low lasing threshold, which we believe is increased by larger loss in the gratings due to the higher fluence required (1 kJ compare to 0.03 kJ). As with the DFB, we see pulsing of the DBR laser, as shown in Fig. 1c. However, most of this is as expected for longitudinal mode beating (repetition rate matches the expected free spectral range) with occasional single-frequency SBS pulses and massive pulse bursts which always lead to pump depletion. It should also be noted that if these lasers are run near threshold they can enter stable CW single or at slightly higher powers quasi-CW dual mode lasing with no SBS. We will report on our latest findings into DBR lasers, optimisation of grating fabrication to improve lasing parameters, further investigations into pulsed behaviour, and potentially cascading using DFB cavities
Dataset for: Short single-frequency self-pulsing Brillouin-Raman distributed feedback fiber laser
No full textDataset for the paper: 'Short single-frequency self-pulsing Brillouin-Raman distributed feedback fiber laser' accepted in Optics Express.
Dataset contains raw data for all the optical/eletronic spectra and oscioscope graphs presented in the paper.</span
Dataset for the paper '375-395nm UV Generation in Zn-indiffused MgO-doped PPLN Waveguides pumped by an Alexandrite Laser'
No full textData used in the paper: 375-395nm UV Generation in Zn-indiffused MgO-doped PPLN Waveguides pumped by an Alexandrite Laser. Data was recorded during 2024 in OEQP group labs at the ORC. Paper DOI: https://doi.org/10.1364/OE.553761</span
Direct UV written integrated waveguides using 213nm light
No full textDirect UV writing is a technique capable of fabricating low-loss channel waveguides, couplers and Bragg gratings in planar silica devices by translating an appropriate substrate through a tightly focused UV beam. To date direct UV written waveguides have been primarily formed using 244nm laser light, relying on the photosensitivity provided by doping with germanium and boron. To induce sufficient refractive index change, necessary for wave guiding, the substrates also require hydrogenation prior to UV writing. Not only does this require additional processing but over time the hydrogen present within the silica out-diffuses, which can cause variation of the final written structures. Deep-UV light, with a wavelength of 213 nm, has previously been used to inscribe strong fibre Bragg gratings (FBGs) in hydrogen-free Ge-doped fibres. Here we present the use of a 213 nm UV laser to write planar waveguide devices without the need for hydrogen loading.Flame Hydrolysis Deposition (FHD) was used to deposit core and cladding layers of doped silica onto a thermally oxidised silicon wafer. Individual planar chips were diced from this wafer and a 5th harmonic Q-switched solid state laser operating at 213 nm wavelength was used to inscribe waveguides within the germanium-doped core layer of the chips without prior hydrogen loading. We shall present our latest results of direct deep-UV written waveguides, including; the characterisation of single mode waveguides, detailed fluence and loss measurements, induced refractive index change and the first demonstration of planar Bragg gratings and photonic structures written with 213nm light
Dataset for Direct UV Written Integrated Planar Waveguides using a 213 nm Laser
No full textDataset containing all data taken and used for 'Direct UV written integrated planar waveguides using a 213 nm laser' published in Optics Express.</span
Dataset for Optical Spectrum with time as temperature is increased for thermally regenerative gratings
No full textDataset supports:
Jantzen, A. et al (2017). Observations from direct UV written, non-hydrogen loaded, thermally regenerated Bragg gratings in double clad photosensitive fiber. Optics Letters, 42(19), 3741-3744.
Experimental data from the temperature annealing of GF4A fiber annealled in an oxygen environment. A series of Bragg gratings had been written into the fiber prior to heating through the method of Direct Ultraviolet Writing. Continuous data collection from an ANDO AQ6317B optical spectrum analyser, recording on mid sensitivity between 1450 nm to 1600 nm at 0.02 nm resolution. Data is recorded every 24 seconds, corresponding to a 2 degrees celsius increase during ramp. Data is labelled, prerun, for the reference before data collection, run1 for the data once heat is introduced to the system and PostRun is the reference once the experiment had concluded. The references are know to be approximately 4 % reflectors and is used to normalise intensity.</span
Direct UV written integrated planar waveguides using a 213 nm laser
No full textWe present the first demonstration of integrated waveguides in planar silica devices fabricated using direct UV writing with 213 nm laser light. Waveguides were produced with different writing fluences and the NA and MFD of each were measured. Single mode waveguides were achieved at fluence values one tenth that typically required when operating with a 244 nm laser, allowing for more rapid fabrication. A maximum in-plane index change of 2.4 x10-3 for a writing fluence of 5 kJ cm-2 was estimated from NA measurements. Finally cutback measurements were performed and a propagation loss of 0.42 ± 0.07 dB/cm was directly measured, though losses as low as 0.2 ± 0.03 dB/cm are indicated through calculations
Dual-process Bragg Grating Inscription in Bulk Fused Silica through Combination of IR Femtosecond and Continuous Wave UV Laser Direct Writing
No full textWe demonstrate femtosecond laser induced photosensitivity allowing to perform direct UV laser writing in pure fused silica, offering new 3D design freedoms. </p
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