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  • Conference paper
    Battle RA, Simon D, Xiang Y, Robinson K, Runcorn TH, Murray RT, Takats Zet al., 2023,

    Cellular Level Resolution Ambient Mass Spectrometry Imaging using 3 µm Laser Ablation

    Tissue can be rapidly ablated by lasers with wavelength around λ = 3 µm, which is strongly absorbed by water [1]. Mass spectrometry (MS) analysis of the ablated material can subsequently provide rich chemical data about the molecular content of the tissue. In mass spectrometry imaging (MSI), spatially resolved molecular data is obtained from a sample by collecting multiple mass spectra. From these individual spectra, the spatial distribution of molecules of interest can be mapped. In this work, we report a single-cell level resolution mass spectrometry imaging platform based on laser ablation using a parametric 3 µm laser source and Rapid Evaporative Ionization Mass Spectrometry (REIMS) [2]. The laser source is specifically developed to have high beam quality and sub-ns duration. This has allowed us to overcome previous ambient MSI spatial resolution limits, a key step to translating the benefits of MS analysis to clinical applications.

  • Conference paper
    Krawczyk B, Kudlinski A, Battle RA, Murray RT, Runcorn THet al., 2023,

    Four-Wave Mixing Enhancement in a Yb-doped Photonic Crystal Fiber

    Degenerate four-wave mixing (FWM) in photonic crystal fibers (PCFs) is an effective method for generating near-infrared coherent light across a wide range of wavelengths using compact, low-cost ytterbium or neodymium pump lasers [1]. For many applications, e.g. multiphoton microscopy, increasing the peak power of the short wavelength anti-Stokes sideband generated by FWM is advantageous. Several works have sought to scale the anti-Stokes peak power by optimizing the pump laser and PCF structure but the pump to anti-Stokes conversion efficiency remains limited by pump depletion [2]. By introducing Yb-doping into the core of a PCF designed for FWM, we propose to mitigate the effects of pump depletion by using stimulated emission to replenish the FWM pump energy that is transferred to the anti-Stokes (and Stokes) as it propagates down the fiber. Here we present a novel double-clad PCF with a Yb-doped core and demonstrate, for the first time to the best of our knowledge, that amplification of FWM pump pulses through stimulated emission increases the anti-Stokes power generated by FWM.

  • Conference paper
    Pearce E, Flórez J, Gemmell NR, Karzazi MA, Ma Y, Bressanini G, Battle RA, Murray RT, Kim MS, Phillips CC, Oulton RF, Clark ASet al., 2023,

    Enhancing Nonlinear Interferometers for Imaging with Undetected Photons: Seeding and High-Gain

    Infrared (IR) imaging and spectroscopy is invaluable to many disciplines for its ability to probe molecular responses, from material analysis to diagnostic medicine. However, these applications are often limited by inefficient, noisy detectors. Non-degenerate nonlinear interferometers (NLIs) offer an alternative route through a technique known as imaging with undetected photons [1]. For an NLI producing visible-IR photon pairs, a change in the IR due to an object can be observed as a change to the interference of the visible photons. The IR does not need to be detected, bypassing the need for IR detectors completely.

  • Conference paper
    Taengnoi N, Bottrill KRH, Hong Y, Wang Y, Sahu J, Hanzo L, Richardson DJ, Petropoulos Pet al., 2023,

    Coherent O-band Transmission of 4×25 GBd DP-16QAM Channels Over a 50 km BDFA-Equipped Link

    The first WDM O-band coherent transmission experiment in a BDFA-amplified link is reported. Four 25 GBd DP16QAM channels (4×200 Gb/s) are transmitted over 50 km of fiber, occupying a bandwidth of 4.7 THz.

  • Conference paper
    Xiao H, Jiang X, Damzen MJ, 2023,

    Alexandrite Lasers Operating with High-power Blue-diode-pumping

    Alexandrite is a solid-state laser with excellent thermal properties for power scaling and together with its broad wavelength tunability (~720-820 nm) provides potential for applications in remote sensing, biophotonics, and quantum technologies. Until recently, diode pumping has been predominantly performed by red semiconductor lasers near 638nm, however, blue diodes operating near 445nm have higher emitter power, higher-brightness and low-cost ($/W) making them attractive as alternative pump sources for Alexandrite lasers. This work focuses on the investigation of Alexandrite lasers pumped by a high-power fibre-delivered blue diode module achieving record blue-pumped powers and provides in-depth laser performance characterisation.

  • Conference paper
    Liang M, Minassian A, Damzen M, 2023,

    Acousto-optic Q-switched Alexandrite Laser with Wavelength Tuning and Second Harmonic Generation

    Alexandrite is an excellent solid-state laser medium for high-power Q-switched operation due to its high thermal conductivity (23 Wm−1K−1) and long upper-state lifetime (262 µs). Whilst electro-optically Q-switched (EO-QS) Alexandrite lasers with red diode-pumping have been demonstrated [1], this work presents results of the first ever Acousto-Optic Q-switched (AO-QS) Alexandrite laser. In addition, we present results of the conversion of the output of the wavelength-tuned AO-QS laser to tunable ultraviolet by second harmonic generation.

  • Conference paper
    Taengnoi N, Bottrill KRH, Hong Y, Wang Y, Sahu J, Hanzo L, Richardson DJ, Petropoulos Pet al., 2023,

    Demonstration of 100-km Long O-band WDM Amplified Coherent Transmission

    O-band WDM 100-Gb/s/λ dual-polarization quadrature phase shift keying transmission is demonstrated over a 100-km link, with gain provided by bismuth-doped fiber amplifiers. Two different channel spacings are studied: 0.6nm and 10nm.

  • Conference paper
    Hong Y, Taengnoi N, Bottrill KRH, Wang Y, Sahu JK, Petropoulos P, Richardson DJ, Calo C, Blache F, Ghazisaeidi A, Renaudier Jet al., 2023,

    Towards Ultra-Wideband Optical Communications Using Novel Optical Amplifiers

    Ultra-wideband transmission over extended bandwidths through the existing fibre infrastructure represents a promising solution. In this paper, we review the recent progress of novel optical amplifiers-enabled ultra-wideband transmission over alternative optical bands.

  • Conference paper
    Murray RT, Wang L, Chen W, Battle RA, Schirrmacher A, Büttner E, Petrov Vet al., 2023,

    Narrowband seeding of a PPLN nonresonant optical parametric oscillator

    , ISSN: 0277-786X

    We present a nanosecond, non-resonant optical parametric oscillator (NRO) based on a 20 mm long periodically-poled LiNbO3 (PPLN) crystal operating at 30-70 kHz. Pumping with a nanosecond Nd:YVO4 laser at 1064 nm in a double-pass configuration, the signal plus idler average output power reached 1.2 W for a pump level of 4 W (at 35 kHz repetition rate). Narrowband seeding with a Tm-fiber laser is employed to narrow the linewidths of the signal to 0.8 nm and the idler to 2 nm. Continuous-wave seed levels as low as 2 mW were sufficient to produce the effect which means that this technique could be useful for single-frequency operation using DFB seed laser diodes. At higher pump power levels > 4 W, the linewidth narrowing effect produced by the seeding was insufficient to prevent broader linewidth operation of the NRO signal and idler outputs. Pumping the NRO at higher repetition rates to scale the average output power of the NRO whilst remaining in the narrow linewidth operation mode is discussed.

  • Conference paper
    Tawy G, Davidson NP, Mennea PL, Churchill G, Wright LD, Bannerman RHS, Smith PGR, Gates JC, Damzen MJ, Gawith CBEet al., 2023,

    375-400nm UV Generation via an Alexandrite laser and Zn-indiffused MgO-doped PPLN Waveguides

    Laser sources in the UV-blue region at around 350-400 nm are of increasing importance for applications including quantum technologies and material processing. To operate in a wide range of environments, these laser sources need to be compact, robust and have low-power and minimal cooling requirements. The work presented here looks at combining rapid progress in two areas of laser development for addressing these applications. Diode-pumped Alexandrite lasers have become a low-cost and simple approach to achieving multi-watt powers in the near-infrared at around 720-800 nm [1]. Zn-indiffused MgO-doped PPLN waveguides have recently demonstrated impressive second harmonic generation (SHG) conversion efficiencies in the near-infrared [2] as well as conversion into the UV with doubling to 390 nm recently reported [3].

  • Journal article
    Koufidis SF, McCall MW, 2022,

    M?bius transformation and coupled-wave theory: Complete identification of the transfer matrix

    , PHYSICAL REVIEW A, Vol: 106, ISSN: 2469-9926
  • Journal article
    Rahman T, Baxan N, Murray R, Tavana S, Schaer T, Smith N, Bull J, Newell Net al., 2022,

    An in vitro comparison of three nucleus pulposus removal techniques for partial intervertebral disc replacement: An ultra-high resolution MRI study

    , JOR Spine, ISSN: 2572-1143
  • Journal article
    McCall M, Koufidis S, 2022,

    Reverse circular Bragg phenomenon

    , Physical Review Research, Vol: 4, ISSN: 2643-1564

    he problem of axial propagation of circularly polarized light in a circularly birefringent structurally chiral medium is exactly solved via full electromagnetic analysis. Underlying symmetries of the system's characteristic matrix reveal interesting insights, which are confirmed by coupled wave theory. For extreme values of chirality, a reverse circular Bragg resonance arises in the negative refraction regime where handedness reversal of counterpart modes occurs. A condition is identified under which circular birefringence precisely offsets structural chirality, rendering the medium simply linearly birefringent. Manufacturing such a medium is feasible via current metamedia and inorganic materials technology and has applications in optics, optoelectronics, and sensing.

  • Journal article
    Hong W, Wright T, Sparks H, Dvinskikh L, MacLeod K, Paterson C, Dunsby Cet al., 2022,

    Adaptive light-sheet fluorescence microscopy with a deformable mirror for video-rate volumetric imaging

    , Applied Physics Letters, Vol: 121, Pages: 1-7, ISSN: 0003-6951

    Light-sheet fluorescence microscopy (LSFM) achieves optically sectioned imaging with the relatively low photobleaching and phototoxic effect. To achieve high-speed volumetric LSFM imaging without perturbing the sample, it is necessary to use some form of remote refocusing in the detection beam path. Previous work used electrically tunable lenses, tunable acoustic gradient index of refraction lenses, or the remote-refocusing approach of Botcherby et al. [Opt. Lett. 32(14), 2007 (2007)] to achieve remote refocusing. However, these approaches generally only provide low-order defocus correction, which is not compatible with higher-NA objectives that require higher order defocus corrections or reduce the optical throughput. In order to simultaneously achieve high-speed remote refocusing and correct system aberrations, we employ a deformable mirror in the detection path that is capable of providing higher orders of defocus and aberration correction in an optical system with an NA of 0.72–0.75. We demonstrate high-speed volumetric imaging at 26.3 volumes per second and 35 frames per volume for a defocus range of −50 to 50 μm.

  • Journal article
    Ribenek VA, Korobko DA, Fotiadi AA, Taylor JRet al., 2022,

    Supermode noise mitigation and repetition rate control in a harmonic mode-locked fiber laser implemented through the pulse train interaction with co-lased CW radiation: publisher's note

    , OPTICS LETTERS, Vol: 47, Pages: 5582-5582, ISSN: 0146-9592
  • Journal article
    Kinsler P, McCall MW, Oulton RF, Clark ASet al., 2022,

    The surprising persistence of time-dependent quantum entanglement

    , New Journal of Physics, Vol: 24, Pages: 1-14, ISSN: 1367-2630

    The mismatch between elegant theoretical models and the detailed experimental reality is particularly pronounced in quantum nonlinear interferometry (QNI). In stark contrast to theory, experiments contain pump beams that start in impure states and that are depleted, quantum noise that affects—and drives—any otherwise gradual build up of the signal and idler fields, and nonlinear materials that are far from ideal and have a complicated time-dependent dispersive response. Notably, we would normally expect group velocity mismatches to destroy any possibility of measurable or visible entanglement, even though it remains intact—the mismatches change the relative timings of induced signal–idler entanglements, thus generating 'which path' information. Using an approach based on the positive-P representation, which is ideally suited to such problems, we are able to keep detailed track of the time-domain entanglement crucial for QNI. This allows us to show that entanglement can be—and is—recoverable despite the obscuring effects of real-world complications; and that recovery is attributable to an implicit time-averaging present in the detection process.

  • Journal article
    Tang M, 2022,

    Super-resolution ultrasound localization microscopy of microvascular structure and flow for distinguishing metastatic lymph nodes – an initial human study

    , Ultraschall in der Medizin, Vol: 43, Pages: 592-598, ISSN: 0172-4614

    Purpose Detecting and distinguishing metastatic lymph nodes (LNs) from those with benign lymphadenopathy are crucial for cancer diagnosis and prognosis but remain a clinical challenge. A recent advance in super-resolution ultrasound (SRUS) through localizing individual microbubbles has broken the diffraction limit and tracking enabled in vivo noninvasive imaging of vascular morphology and flow dynamics at a microscopic level. In this study we hypothesize that SRUS enables quantitative markers to distinguish metastatic LNs from benign ones in patients with lymphadenopathy.Materials and Methods Clinical contrast-enhanced ultrasound image sequences of LNs from 6 patients with lymph node metastasis and 4 with benign lymphadenopathy were acquired and motion-corrected. These were then used to generate super-resolution microvascular images and super-resolved velocity maps. From these SRUS images, morphological and functional measures were obtained including micro-vessel density, fractal dimension, mean flow speed, and Local Flow Direction Irregularity (LFDI) measuring the variance in local flow direction. These measures were compared between pathologically proven reactive and metastasis LNs.Results Our initial results indicate that the difference in the indicator of flow irregularity (LFDI) derived from the SRUS images is statistically significant between the two groups. The LFDI is 60% higher in metastatic LNs compared with reactive nodes.Conclusion This pilot study demonstrates the feasibility of super-resolution ultrasound for clinical imaging of lymph nodes and the potential of using the irregularity of local blood flow directions afforded by SRUS for the characterization of LNs.

  • Journal article
    Ribenek VA, Korobko DA, Fotiadi AA, Taylor JRet al., 2022,

    Supermode noise mitigation and repetition rate control in harmonic mode-locked fiber laser implemented through the pulse train interaction with co-lased CW radiation

    , OPTICS LETTERS, Vol: 47, Pages: 5236-5239, ISSN: 0146-9592
  • Journal article
    Hong Y, Taengnoi N, Bottrill KRH, Thipparapu NK, Wang Y, Sahu JK, Richardson DJ, Petropoulos Pet al., 2022,

    Experimental demonstration of single-span 100-km O-band 4×50-Gb/s CWDM direct-detection transmission.

    , Opt Express, Vol: 30, Pages: 32189-32203

    We report on what is to the best of our knowledge the longest 50-Gb/s/λ O-band wavelength-division multiplexed (WDM) transmission. A pair of in-house built bismuth-doped fiber amplifiers (BDFAs) and the use of Kramers-Kronig detection-assisted single-sideband transmission are adopted to overcome the fiber loss and chromatic dispersion, respectively, in a reach-extended O-band coarse WDM (CWDM) system with a channel spacing of ∼10 nm. Through experiments on an amplified 4×50-Gb/s/λ direct-detection system based on booster and pre-amp BDFAs, we show the superior performance of single-sideband transmission in terms of both optical signal-to-noise ratio sensitivity and uniformity in performance amongst CWDM channels relative to double-sideband transmission after both 75-km and 100-km lengths of single-mode fiber. As a result, up to 100-km reach with comparable performance at all 50-Gb/s channels was achieved without the need for in-line optical amplification.

  • Journal article
    Calvarese M, Paie P, Candeo A, Calisesi G, Ceccarelli F, Valentini G, Osellame R, Gong H, Neil M, Bragheri F, Bassi Aet al., 2022,

    Integrated optical device for Structured Illumination Microscopy

    , OPTICS EXPRESS, Vol: 30, Pages: 30246-30259, ISSN: 1094-4087
  • Journal article
    Coney AT, Beecher S, Damzen MJ, Elder Iet al., 2022,

    High-energy Q-switched Nd:YAG oscillator and amplifier development for large-mode, low-alignment sensitivity applications

    , LASER PHYSICS LETTERS, Vol: 19, ISSN: 1612-2011
  • Journal article
    Lightley J, Kumar S, Garcia E, Alexandrov Y, Dunsby C, Neil MAA, French PMWet al., 2022,

    Robust, single-shot, optical autofocus system utilizing cylindrical lenses to provide high precision and long range of operation

    <jats:title>ABSTRACT</jats:title><jats:p>We present a robust, “real-time” optical autofocus system for microscopy that provides high accuracy (&lt;230 nm) and long range (∼130 µm) with a 1.4 numerical aperture oil immersion objective lens. This autofocus can operate in a closed loop, single-shot functionality over a range of ±37.5 µm and can also operate as a 2-step process up to ±68 µm. A real-time autofocus capability is useful for experiments with long image data acquisition times, including single molecule localization microscopy, that may be impacted by defocusing resulting from drift of components, e.g., due to changes in temperature or mechanical drift. It is also vital for automated slide scanning or multiwell plate imaging where the sample may not be in the same horizontal plane for every field of view during the image data acquisition. To realise high precision and long range, we implement orthogonal optical readouts using cylindrical lenses. We demonstrate the performance of this new optical autofocus system with automated multiwell plate imaging and single molecule localisation microscopy and illustrate the benefit of using a superluminescent diode as the autofocus light source.</jats:p>

  • Journal article
    Thipparapu NK, Alam S, Wang Y, Pidishety S, Richardson DJ, Sahu JKet al., 2022,

    Widely Tunable Actively Mode-Locked Bi-Doped Fiber Laser Operating in the O-Band

    , IEEE Photonics Technology Letters, Vol: 34, Pages: 711-714, ISSN: 1041-1135

    Here, we propose an all-fiber actively mode-locked Bismuth (Bi)-doped fiber laser based on the use of an acousto-optic modulator. The mode-locked Bi-doped fiber laser produces 13ns pulses with a repetition rate of 1.683MHz at 1340nm. Higher harmonic mode-locking is achieved simply by changing the operating frequency of the acousto-optic modulator. The output power of the laser is 7mW and this is further amplified to 101mW using an external Bi-doped fiber amplifier. A peak power of 4.6W with a pulse energy of 60nJ is achieved after the master oscillator power amplifier. The stability of the laser is studied using an RF spectrum analyzer and an SNR of more than 60dB at the fundamental frequency of 1.683MHz was recorded. Furthermore, wavelength tuning of the Bi-doped fiber laser is explored and demonstrated from 1300 to 1370nm.

  • Journal article
    Chung CH, Li J, Steuer CE, Bhateja P, Johnson M, Masannat J, Poole MI, Song F, Hernandez-Prera JC, Molina H, Wenig BM, Kumar S, Kuperwasser C, Stephens PJ, Farinhas JM, Shin DM, Kish JA, Muzaffar J, Kirtane K, Rocco JW, Schell MJ, Saba NF, Bonomi Met al., 2022,

    Phase II Multi-institutional Clinical Trial Result of Concurrent Cetuximab and Nivolumab in Recurrent and/or Metastatic Head and Neck Squamous Cell Carcinoma.

    , Clin Cancer Res, Vol: 28, Pages: 2329-2338

    PURPOSE: A phase II multi-institutional clinical trial was conducted to determine overall survival (OS) in patients with recurrent and/or metastatic (R/M) head and neck squamous cell carcinoma (HNSCC) treated with a combination of cetuximab and nivolumab. PATIENTS AND METHODS: Patients with R/M HNSCC were treated with cetuximab 500 mg/m2 i.v. on day 14 as a lead-in followed by cetuximab 500 mg/m2 i.v. and nivolumab 240 mg i.v. on day 1 and day 15 of each 28-day cycle. Expression of p16 and programmed cell death-ligand 1 (PD-L1) in archived tumors were determined. Tumor-tissue-modified human papillomavirus (TTMV) DNA was quantified in plasma. RESULTS: Ninety-five patients were enrolled, and 88 patients were evaluable for OS with a median follow-up of 15.9 months. Median OS in the 45 patients who had prior therapy for R/M HNSCC (cohort A) was 11.4 months, with a 1 year OS 50% [90% confidence interval (CI), 0.43-0.57]. Median OS in the 43 patients who had no prior therapy (cohort B) was 20.2 months, with a 1-year OS 66% (90% CI, 0.59-0.71). In the combined cohorts, the p16-negative immunostaining was associated with higher response rate (RR; P = 0.02) but did not impact survival while higher PD-L1 combined positive score was associated with higher RR (P = 0.03) and longer OS (log-rank P = 0.04). In the p16-positive patients, lower median (1,230 copies/mL) TTMV DNA counts were associated with higher RR (P = 0.01) and longer OS compared with higher median (log-rank P = 0.05). CONCLUSIONS: The combination of cetuximab and nivolumab is effective in patients with both previously treated and untreated R/M HNSCC and warrants further evaluation.

  • Journal article
    Van de Pette M, Dimond A, Galvao AM, Millership SJ, To W, Prodani C, McNamara G, Bruno L, Sardini A, Webster Z, McGinty J, French PMW, Uren AG, Castillo-Fernandez J, Watkinson W, Ferguson-Smith AC, Merkenschlager M, John RM, Kelsey G, Fisher Aet al., 2022,

    Epigenetic changes induced by in utero dietary challenge result in phenotypic variability in successive generations of mice

    , Nature Communications, Vol: 13, ISSN: 2041-1723

    Transmission of epigenetic information between generations occurs in nematodes, flies and plants, mediated by specialised small RNA pathways, modified histones and DNA methylation. Similar processes in mammals can also affect phenotype through intergenerational or trans-generational mechanisms. Here we generate a luciferase knock-in reporter mouse for the imprinted Dlk1 locus to visualise and track epigenetic fidelity across generations. Exposure to high-fat diet in pregnancy provokes sustained re-expression of the normally silent maternal Dlk1 in offspring (loss of imprinting) and increased DNA methylation at the somatic differentially methylated region (sDMR). In the next generation heterogeneous Dlk1 mis-expression is seen exclusively among animals born to F1-exposed females. Oocytes from these females show altered gene and microRNA expression without changes in DNA methylation, and correct imprinting is restored in subsequent generations. Our results illustrate how diet impacts the foetal epigenome, disturbing canonical and non-canonical imprinting mechanisms to modulate the properties of successive generations of offspring.

  • Conference paper
    Wysoczanski R, Baker JR, Fenwick P, Alexandrov Y, Dunsby C, French P, Barnes PJ, Donnelly LEet al., 2022,

    Defective Phagocytosis in COPD Macrophages Is Improved by Mitochondrial Antioxidants Without Alteration in Mitochondrial Function

    , International Conference of the American-Thoracic-Society, Publisher: AMER THORACIC SOC, ISSN: 1073-449X
  • Journal article
    Ahmad H, Hidayah Abdul Kahar N, Yusoff N, Zharif Samion M, Aisyah Reduan S, Faizal Ismail M, Bayang L, Wang Y, Wang S, Sahu JKet al., 2022,

    Passively Q-switched 1.3 μm bismuth doped-fiber laser based on transition metal dichalcogenides saturable absorbers

    , Optical Fiber Technology, Vol: 69, ISSN: 1068-5200

    In this work, Q-switched fiber laser has been demonstrated in a bismuth-doped fiber laser (BDFL) system using tungsten ditelluride (WTe2) and tungsten disulfide (WS2) as saturable absorbers (SAs). The solution casting method was used to prepare both WTe2 and WS2 thin films SAs. At the threshold pump power, the generation of Q-switched pulse using WTe2 SA resulted in a pulse width of 10.4μ s and a repetition rate of 21.20 kHz. When the pump power was increased to maximum, the pulse width reduced to 8.0μ s, while the repetition rates increased to 22.46 kHz. Similarly, a Q-switched pulse was generated using WS2 SA, with an initial repetition rate of 18.86 kHz and a pulse width of 14.4μ s. The repetition rate of the pulses then increased to 19.53 kHz and pulse width reduced to 11.2 μs with the increasing pump power. The maximum pulse energy obtained for WTe2 and WS2 SAs was 13.93 nJ and 11.36 nJ, respectively, with a maximum average output power of 0.313 mW (WTe2) and 0.222 mW (WS2). This work uses the transition metal dichalcogenides (TMDs) materials to generate Q-switched pulses in BDFL operating at 1.3 µm region.

  • Journal article
    Tawy G, Minassian A, Damzen MJ, 2022,

    Volume Bragg Grating Locked Alexandrite Laser

    , Optics, Vol: 3, Pages: 53-59

    We report the first ever demonstration of a wavelength-locked Alexandrite laser using a volume Bragg grating (VBG) as a wavelength-selective mirror. Output power of 3.3 W with a diffraction limited beam quality of M (Formula presented.) was obtained at a lasing wavelength of 762.2 nm and a linewidth (FWHM) of 2.5 GHz.

  • Journal article
    Hong W, Dunsby C, 2022,

    Automatic tube lens design from stock optics for microscope remote-refocusing systems

    , Optics Express, Vol: 30, Pages: 4274-4278, ISSN: 1094-4087

    The remote-refocusing approach of Botcherby et al. [Opt. Lett. 32, 2007 (2007) [CrossRef] ] has been applied widely to 2D and 3D fluorescence microscopes to enable rapid refocusing of the optical system without mechanically perturbing the sample. In order for this approach to operate correctly, it requires that the overall magnification of the first two microscope systems matches the ratio of the refractive indices in sample and intermedia image spaces. However, commercially available tube lenses are not always suitable to produce the desired overall magnification. Therefore, a practical approach to produce tube lenses with low expense and diffraction-limited performance is required. Tube lenses can be formed using a pair of stock achromatic doublets, however, selecting appropriate pairs of achromatic doublets from stock optics is a time-consuming process, as many combinations can be considered. In this paper, we present two software packages (Catalogue Generator and Doublet Selector) developed in MATLAB that use the application programming interface (ZOS-API) to the Zemax OpticStudio optical design software to realise an automatic search of stock achromatic doublets to produce microscope tube lenses with a specified focal length, entrance pupil diameter and maximum design field angle. An algorithm to optimise principal plane positions in versions of OpticStudio before 20.2 was also introduced to enable the use of older software versions. To evaluate the performance of Catalogue Generator and Doublet Selector, we used them to generate ten tube lens designs. All of the software-produced tube lenses have a better optical performance than those using manually selected pairs of stock doublets lenses.

  • Journal article
    Hong Y, Deligiannidis S, Taengnoi N, Bottrill KRH, Thipparapu NK, Wang Y, Sahu JK, Richardson DJ, Mesaritakis C, Bogris A, Petropoulos Pet al., 2022,

    ML-Assisted Equalization for 50-Gb/s/λ O-Band CWDM Transmission Over 100-km SMF

    , IEEE Journal of Selected Topics in Quantum Electronics, Vol: 28, ISSN: 1077-260X

    We propose and demonstrate a bidirectional Vanilla recurrent neural network (Vanilla-RNN) based equalization scheme for O-band coarse wavelength division multiplexed (CWDM) transmission. Based on a 4 × 50-Gb/s intensity modulation and direct detection (IM/DD) system, we demonstrate the significantly better bit error rate (BER) performance of the Vanilla-RNN scheme over the conventional decision feedback equalizer (DFE) for both Nyquist on-off keying (OOK) and Nyquist 4-ary pulse amplitude modulation (PAM4) formats. It is shown that the Vanilla-RNN equalizer is capable of compensating for both linear and nonlinear impairments induced by the transceiver and the single-mode fiber (SMF). As a result, up to 100-km and 75-km SMF transmission can be achieved for OOK and PAM4 transmission, respectively. Furthermore, through the comparison with other equalization schemes, including the linear equalizer, 3rd-order Volterra equalizer, and Volterra+DFE, it is demonstrated that the Vanilla-RNN equalizer achieves the best BER performance. In the meantime, it also exhibits lower implementation complexity when compared to Volterra-based schemes. Our results show that the Vanilla-RNN scheme is a viable solution for realizing simple and effective equalization. This work serves as an exploration and offers useful insights for future implementations of reach-extended O-band CWDM IM/DD systems.

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