pith. machine review for the scientific record. sign in

arxiv: 2605.02088 · v1 · submitted 2026-05-03 · ⚛️ physics.optics

Recognition: 2 theorem links

Sapphire Photonic Crystal Fiber Sensor

Mohan Wang , Tongyu Liu , Zipei Song , Richard Reeves , Frank P. Payne , Igor N. Dyson , Kaihui Zhang , Tao Wang
show 5 more authors
Jian Zhang Zhitai Jia Patrick S. Salter Martin J. Booth Julian A. J. Fells
Authors on Pith no claims yet

Pith reviewed 2026-05-08 19:12 UTC · model grok-4.3

classification ⚛️ physics.optics
keywords sapphire fiberphotonic crystal waveguidefiber Bragg gratingtemperature sensorfemtosecond laser inscriptionhigh-temperature sensingextreme environment monitoring
0
0 comments X

The pith

Femtosecond laser writing creates index-guiding sapphire photonic crystal fiber Bragg gratings for high-temperature sensing up to 1200°C.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows how to fabricate longer sapphire fiber sensors by inscribing a photonic crystal waveguide and Bragg grating directly with a femtosecond laser while using a spatial light modulator to correct for optical mismatch and prevent cracking. This method cuts fabrication time by a factor of six compared to earlier depressed-cladding designs and produces devices up to 7 cm long that can be spliced to ordinary single-mode fiber. The resulting sensors exhibit 0.7 dB/cm propagation loss, 0.12 nm grating bandwidth, and temperature sensitivity between 19.0 and 32.3 pm/°C across 25–1200°C when tested in a furnace. A reader would care because these improvements move sapphire fiber sensors closer to routine use in extreme environments where conventional sensors fail.

Core claim

By applying femtosecond laser direct writing with spatial light modulator compensation, an index-guiding photonic crystal structure and integrated Bragg grating can be formed inside sapphire fiber to produce devices as long as 7 cm. These devices splice to standard single-mode fiber, show 0.7 dB/cm loss and 0.12 nm bandwidth, and deliver temperature sensitivities of 19.0–32.3 pm/°C over 25–1200°C, offering a six-fold reduction in fabrication time relative to previous depressed-cladding waveguides.

What carries the argument

Femtosecond laser direct writing with spatial light modulator compensation that simultaneously forms an index-guiding photonic crystal waveguide and a Bragg grating inside the sapphire fiber.

Load-bearing premise

The laser-inscribed photonic crystal waveguides remain crack-free, single-mode, and keep stable Bragg gratings after splicing and repeated exposure to 1200°C.

What would settle it

Cracking visible in the waveguide cross-section or more than a few picometers of irreversible Bragg wavelength drift after 100 hours at 1200°C would show the central claim does not hold.

Figures

Figures reproduced from arXiv: 2605.02088 by Frank P. Payne, Igor N. Dyson, Jian Zhang, Julian A. J. Fells, Kaihui Zhang, Martin J. Booth, Mohan Wang, Patrick S. Salter, Richard Reeves, Tao Wang, Tongyu Liu, Zhitai Jia, Zipei Song.

Figure 2
Figure 2. Figure 2: Confinement loss versus number of cladding layers in PCF with an 8 µm lattice pitch and a core with 7 missing tracks. A design with 7 missing tracks in the lattice was therefore chosen, with an example simulated mode profile shown in view at source ↗
Figure 3
Figure 3. Figure 3: Dependence of the fundamental-mode MFD on lattice constant for different track refractive indices. The core had 7 missing tracks view at source ↗
Figure 4
Figure 4. Figure 4: Confinement loss of the fundamental and higher-order spatial modes versus lattice constant for a laser-induced refractive index change of -0.003. The core had 7 missing tracks. Further analysis considers the loss behavior of the fundamental and higher-order modes, thereby providing a more complete assessment of the guiding performance and mode-selective properties of the fiber view at source ↗
Figure 5
Figure 5. Figure 5: Diagram illustrating the equivalent interface between the oil￾immersion objective (n1) and the high index immersion oil (n2) used. It is noted that ΦSA(𝜌) also includes a defocus term, which shifts the beam position from the actual focal depth, 𝐷𝑎𝑐𝑡 , to the nominal focal depth, 𝐷𝑛𝑜𝑚. To avoid complicated phase patterns, this defocus term is explicitly expressed and subtracted. The defocus term can be foun… view at source ↗
Figure 6
Figure 6. Figure 6: (a, b) Cross-sectional images of laser-modified tracks fabricated with pulse energies ranging from 15 to 100 nJ, (a) without aberration correction and (b) with aberration correction. (c) Aspect ratio of the tracks, calculated from the measured height and width as a function of pulse energy. (d, e) Cross-sectional images of a 150-μm diameter sapphire photonic crystal fiber, fabricated (d) without and (e) wi… view at source ↗
Figure 7
Figure 7. Figure 7: (d). The MFD of a standard single-mode fiber (10.4 μm) is also indicated by the black dashed line. Optimized mode field matching could be achieved using a photonic crystal waveguide with a lattice constant of 4 μm, fabricated with pulse energies of 30 nJ or 45 nJ. The corresponding mode field mismatch loss was calculated to be less than 0.1 dB. However, cracks were observed along the lattice due to the den… view at source ↗
Figure 8
Figure 8. Figure 8: (a) Microscope images of photonic crystal waveguides after annealing at 1200ºC with varying outer layer numbers between 2 to 5, the lattice constant is 8 µm; the scale bar represents 20 μm; (b) the corresponding measured 1550-nm mode fields of the photonic crystal waveguides; the scale bars represent 10 μm; (c) the mode field mismatch loss (blue square) and total loss (orange diamond) dependence on the lay… view at source ↗
Figure 12
Figure 12. Figure 12: Splicer microscope images of the joint after fusion splicing. The 125- μm-diameter SMF-28e+ fiber is on the left and the 150-μm-diameter sapphire FBG sensor is on the right. The photonic crystal waveguide can be identified in the image view at source ↗
Figure 11
Figure 11. Figure 11: The cross-sectional image of a 7-cm sapphire FBG, showing the grating in the middle. C. Fusion splicing To realize a practically deployable sapphire photonic crystal FBG temperature sensor, the sapphire fiber was fusion spliced to a standard single-mode silica fiber (Corning SMF-28e+, or equivalent). Since the sapphire fiber has a rounded hexagonal outer profile and a diameter of 150 μm, which is slightly… view at source ↗
Figure 14
Figure 14. Figure 14: Spectra of the 7 cm sapphire FBG sensor at different temperatures between 100 ℃ to 700 ℃ view at source ↗
Figure 15
Figure 15. Figure 15: Spectra of the 4 cm sapphire FBG sensor at different temperatures view at source ↗
Figure 16
Figure 16. Figure 16: Characterization curve of the 4 cm sapphire FBG sensor at different temperatures. Due to the limited yield of the 7 cm samples, multiple 4 cm long samples were also fabricated for high-temperature testing in order to obtain sufficient experimental data view at source ↗
read the original abstract

Sapphire optical fiber shows great promise for remote sensing in extreme environments approaching 2000 degC, by using laser-processing to form a single-mode waveguide within it. However, for practical application, longer devices with high manufacturability and reliability are required. We report the design, modeling, fabrication, and optimization of an index-guiding sapphire photonic crystal fiber Bragg grating temperature sensor. The device is fabricated using femtosecond laser direct writing to inscribe both the photonic crystal waveguide and the Bragg grating. A spatial light modulator was used to compensate for the mismatch between the immersion objective and the high-index oil used. This improved the aspect ratio and suppressed cracking during fabrication, for higher reliability. The design results in a 6-fold reduction in fabrication time over an equivalent depressed cladding waveguide, significantly reducing the cost of manufacture. Devices up to 7 cm long were fabricated and spliced to standard single-mode fiber. The propagation loss was estimated to be 0.7 dB/cm and the Bragg gratings had a bandwidth of approximately 0.12 nm. Devices were tested in a furnace showing a temperature sensitivity of between 19.0-32.3 pm/degC over a range 25-1200 degC. These longer devices have the potential to enable practical high precision extreme temperature monitoring in many applications, with lower manufacturing cost and higher reliability.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

3 major / 0 minor

Summary. The manuscript reports the design, modeling, fabrication, and high-temperature testing of an index-guiding sapphire photonic crystal fiber (PCF) Bragg grating temperature sensor. Femtosecond laser direct writing with spatial light modulator compensation is used to inscribe both the PCF waveguide and grating, yielding crack-free structures up to 7 cm long that are spliced to standard single-mode fiber. Key results include an estimated propagation loss of 0.7 dB/cm, grating bandwidth of ~0.12 nm, a claimed 6-fold reduction in fabrication time relative to depressed-cladding waveguides, and measured temperature sensitivity of 19.0–32.3 pm/°C over 25–1200 °C.

Significance. If the waveguides are verifiably single-mode and low-loss, the work demonstrates a practical route to longer, more manufacturable sapphire fiber sensors for extreme environments. The experimental achievement of 7 cm devices that survive splicing and furnace testing to 1200 °C, together with the SLM-enabled fabrication improvement, represents a concrete advance in device length and reliability that could support remote sensing applications in aerospace and energy systems.

major comments (3)
  1. [Abstract] Abstract: The propagation loss is reported as 'estimated to be 0.7 dB/cm' for devices up to 7 cm long, yet no measurement protocol (cut-back, transmission fitting, splice-loss subtraction, or length-dependent data) or supporting spectra are supplied. This detail is load-bearing for the central claim that the inscribed PCF waveguides are functional and low-loss.
  2. [Abstract] Abstract: No mode-field profiles, far-field patterns, or other confirmation of single-mode operation is provided for the 7 cm PCF devices, despite the design being an index-guiding photonic crystal structure. Without this, it is impossible to verify that the reported sensitivity and splicing results arise from the intended single-mode waveguides rather than multimode or defective structures.
  3. [Abstract] Abstract: The temperature sensitivity is stated as the range 19.0–32.3 pm/°C with no error bars, full calibration curves, statistical analysis, or explanation of the variation (device-to-device or temperature-dependent). Similarly, the 6-fold fabrication-time reduction lacks quantitative comparison (pulse counts, scan times, or line counts) to the depressed-cladding reference.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive and detailed comments, which help us improve the clarity and completeness of the manuscript. We address each major comment below and will make the indicated revisions to strengthen the presentation of our results on the sapphire PCF Bragg grating sensor.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The propagation loss is reported as 'estimated to be 0.7 dB/cm' for devices up to 7 cm long, yet no measurement protocol (cut-back, transmission fitting, splice-loss subtraction, or length-dependent data) or supporting spectra are supplied. This detail is load-bearing for the central claim that the inscribed PCF waveguides are functional and low-loss.

    Authors: We agree that the abstract would benefit from additional detail on the loss estimation. The full manuscript describes the estimation via transmission measurements with splice-loss subtraction to the standard single-mode fiber. We will revise the abstract to briefly note the protocol and include representative transmission spectra in the revised manuscript or supplementary material. revision: yes

  2. Referee: [Abstract] Abstract: No mode-field profiles, far-field patterns, or other confirmation of single-mode operation is provided for the 7 cm PCF devices, despite the design being an index-guiding photonic crystal structure. Without this, it is impossible to verify that the reported sensitivity and splicing results arise from the intended single-mode waveguides rather than multimode or defective structures.

    Authors: We acknowledge the value of direct experimental confirmation. The manuscript presents design and modeling results predicting single-mode guidance for the chosen photonic crystal parameters. To address this point, we will add mode-field or far-field characterization data for the fabricated 7 cm devices in the revised manuscript. revision: yes

  3. Referee: [Abstract] Abstract: The temperature sensitivity is stated as the range 19.0–32.3 pm/°C with no error bars, full calibration curves, statistical analysis, or explanation of the variation (device-to-device or temperature-dependent). Similarly, the 6-fold fabrication-time reduction lacks quantitative comparison (pulse counts, scan times, or line counts) to the depressed-cladding reference.

    Authors: We will expand the results section to include error bars on the sensitivity values, representative full calibration curves, and a brief statistical summary of device-to-device variation. For the fabrication-time claim, we will insert quantitative comparisons of pulse counts, scan times, and inscribed line counts between the PCF and depressed-cladding processes to substantiate the reported improvement. revision: yes

Circularity Check

0 steps flagged

No circularity in experimental fabrication report

full rationale

The manuscript is a purely experimental report on the design, femtosecond-laser fabrication, splicing, and high-temperature testing of sapphire photonic-crystal fiber Bragg-grating sensors. No mathematical derivation chain, first-principles prediction, or fitted-parameter result is presented that could reduce to its own inputs by construction. The stated 6-fold fabrication-time reduction is a direct comparison of two physical writing strategies, not a derived quantity. Propagation loss (0.7 dB/cm), grating bandwidth (0.12 nm), and temperature sensitivity (19.0–32.3 pm/°C) are reported as measured outcomes of fabricated devices, not as outputs of any self-referential model or self-citation. Consequently the paper contains no load-bearing step of the enumerated circularity patterns.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Experimental fabrication paper with no mathematical model; relies on standard optics and laser-material interaction assumptions without introducing new free parameters or entities.

pith-pipeline@v0.9.0 · 5581 in / 1103 out tokens · 35160 ms · 2026-05-08T19:12:22.671482+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

41 extracted references · 39 canonical work pages

  1. [1]

    Sapphire Fiber Bragg Grating Sensor Made Using Femtosecond Laser Radiation for Ultrahigh Temperature Applications,

    D. Grobnic, S. J. Mihailov, C. W. Smelser, and H. Ding, “Sapphire Fiber Bragg Grating Sensor Made Using Femtosecond Laser Radiation for Ultrahigh Temperature Applications,” IEEE Photon. Technol. Lett., vol. 16, no. 11, Nov. 2004, doi: 10.1109/LPT.2004.834920

    work page doi:10.1109/lpt.2004.834920 2004

  2. [2]

    Sapphire fiber Bragg gratings for high temperature and dynamic temperature diagnostics,

    T. Habisreuther, T. Elsmann, Z. Pan, A. Graf, R. Willsch, and M. A. Schmidt, “Sapphire fiber Bragg gratings for high temperature and dynamic temperature diagnostics,” Appl. Therm. Eng., vol. 91, pp. 860–865, Dec. 2015, doi: 10.1016/j.applthermaleng.2015.08.096

    work page doi:10.1016/j.applthermaleng.2015.08.096 2015

  3. [3]

    Reliable wavelength detection method of sapphire fiber Bragg gratings using added multimode fiber,

    Z. Li et al., “Reliable wavelength detection method of sapphire fiber Bragg gratings using added multimode fiber,” Opt. Laser Technol., 9 Wang and Liu et al. vol. 182, p. 112185, Apr. 2025, doi: 10.1016/j.optlastec.2024.112185

    work page doi:10.1016/j.optlastec.2024.112185 2025

  4. [4]

    Metrological Characterization of a High- Temperature Hybrid Sensor Using Thermal Radiation and Calibrated Sapphire Fiber Bragg Grating for Process Monitoring in Harsh Environments,

    R. Eisermann et al., “Metrological Characterization of a High- Temperature Hybrid Sensor Using Thermal Radiation and Calibrated Sapphire Fiber Bragg Grating for Process Monitoring in Harsh Environments,” Sensors, vol. 22, no. 3, p. 1034, Jan. 2022, doi: 10.3390/s22031034

    work page doi:10.3390/s22031034 2022

  5. [5]

    Cascaded Sapphire Fiber Bragg Gratings Inscribed by Femtosecond Laser for Molten Steel Studies,

    D. R. Alla et al., “Cascaded Sapphire Fiber Bragg Gratings Inscribed by Femtosecond Laser for Molten Steel Studies,” IEEE Trans. Instrum. Meas., vol. 73, pp. 1–8, 2024, doi: 10.1109/TIM.2023.3335530

    work page doi:10.1109/tim.2023.3335530 2024

  6. [6]

    Reimer, Scanning Electron Microscopy: Physics of Image Formation and Microanalysis, Second Edition, Meas

    D. Grobnic, S. J. Mihailov, H. Ding, F. Bilodeau, and C. W. Smelser, “Single and low order mode interrogation of a multimode sapphire fibre Bragg grating sensor with tapered fibres,” Meas. Sci. Technol., vol. 17, no. 5, pp. 980–984, May 2006, doi: 10.1088/0957- 0233/17/5/S07

    work page doi:10.1088/0957- 2006

  7. [7]

    High-Order Mode Suppression in Sapphire Fiber Bragg Gratings Based on Mode Field Matching Fusion Splicing for Single-Mode Demodulation Systems,

    Q. Bian, H. Zhu, J. Liang, Y. Yu, and P. Yan, “High-Order Mode Suppression in Sapphire Fiber Bragg Gratings Based on Mode Field Matching Fusion Splicing for Single-Mode Demodulation Systems,” IEEE Sens. J., vol. 23, no. 15, pp. 16953–16959, Aug. 2023, doi: 10.1109/JSEN.2023.3289933

    work page doi:10.1109/jsen.2023.3289933 2023

  8. [8]

    Quasi-single-mode signal output of sapphire fibre Bragg grating based on single mode fibre offset coupling measurement,

    X. Niu, J. Si, Y. Li, D. Zhang, and T. Chen, “Quasi-single-mode signal output of sapphire fibre Bragg grating based on single mode fibre offset coupling measurement,” Meas. Sci. Technol., vol. 36, no. 9, p. 095206, Sep. 2025, doi: 10.1088/1361-6501/ae0752

    work page doi:10.1088/1361-6501/ae0752 2025

  9. [9]

    Single-mode sapphire fiber Bragg grating high- temperature sensor,

    J. Wu et al., “Single-mode sapphire fiber Bragg grating high- temperature sensor,” Photonics Res., vol. 13, no. 12, p. 3374, Dec. 2025, doi: 10.1364/PRJ.570273

    work page doi:10.1364/prj.570273 2025

  10. [10]

    Fiber Bragg grating fabricated in micro-single-crystal sapphire fiber,

    S. Yang, D. Homa, G. Pickrell, and A. Wang, “Fiber Bragg grating fabricated in micro-single-crystal sapphire fiber,” Opt. Lett., vol. 43, no. 1, p. 62, Jan. 2018, doi: 10.1364/OL.43.000062

    work page doi:10.1364/ol.43.000062 2018

  11. [11]

    High temperature sensing using higher-order-mode rejected sapphire fiber gratings,

    C. Zhan, J. H. Kim, S. Yin, P. Ruffin, and C. Luo, “High temperature sensing using higher-order-mode rejected sapphire fiber gratings,” Optical Memory and Neural Networks, vol. 16, no. 4, pp. 204–210, Dec. 2007, doi: 10.3103/S1060992X07040030

    work page doi:10.3103/s1060992x07040030 2007

  12. [12]

    Single-Mode Helical Sapphire Bragg Grating for High-Temperature Sensing,

    X. Xu et al., “Single-Mode Helical Sapphire Bragg Grating for High-Temperature Sensing,” J. Lightwave Technol., vol. 43, no. 6, pp. 2982–2987, Mar. 2025, doi: 10.1109/JLT.2024.3503579

    work page doi:10.1109/jlt.2024.3503579 2025

  13. [13]

    Single-mode θ- shaped Sapphire Fiber Bragg Grating for High Temperature Sensing,

    C. He, Y. Liu, J. Wu, J. Cai, G. Wang, and X. Shu, “Single-mode θ- shaped Sapphire Fiber Bragg Grating for High Temperature Sensing,” in CLEO 2025, Washington, D.C.: Optica Publishing Group, 2025, p. AA115_2. doi: 10.1364/CLEO_AT.2025.AA115_2

    work page doi:10.1364/cleo_at.2025.aa115_2 2025

  14. [14]

    A Narrow-Band Sapphire Fiber Bragg Grating High- Temperature Sensor Based on Decreasing-Ring Structure,

    X. Zhu et al., “A Narrow-Band Sapphire Fiber Bragg Grating High- Temperature Sensor Based on Decreasing-Ring Structure,” J. Lightwave Technol., pp. 1–9, 2026, doi: 10.1109/JLT.2026.3665819

    work page doi:10.1109/jlt.2026.3665819 2026

  15. [15]

    Creation of an Internal Cladding in Sapphire Optical Fiber Using the 6Li(n,α)3H Reaction,

    B A Wilson and T E Blue, “Creation of an Internal Cladding in Sapphire Optical Fiber Using the 6Li(n,α)3H Reaction,” IEEE Sens. J., vol. 17, no. 22, pp. 7433–7439, 2017

    2017

  16. [16]

    Hybrid Growth of Clad Crystalline Sapphire Fibers for Ultra-High- Temperature (>1500 °C) Fiber Optic Sensors,

    M. A. Kabir, K.-C. Wu, K.-T. Chou, F. Luo, and S. Yin, “Hybrid Growth of Clad Crystalline Sapphire Fibers for Ultra-High- Temperature (>1500 °C) Fiber Optic Sensors,” Photonics, vol. 12, no. 4, p. 299, Mar. 2025, doi: 10.3390/photonics12040299

    work page doi:10.3390/photonics12040299 2025

  17. [17]

    Sapphire photonic crystal fibers,

    N. Pfeiffenberger, “Sapphire photonic crystal fibers,” Optical Engineering, vol. 49, no. 9, p. 090501, Sep. 2010, doi: 10.1117/1.3483908

    work page doi:10.1117/1.3483908 2010

  18. [18]

    Single-mode sapphire fiber Bragg grating,

    M. Wang et al., “Single-mode sapphire fiber Bragg grating,” Opt. Express, vol. 30, no. 9, p. 15482, Apr. 2022, doi: 10.1364/OE.446664

    work page doi:10.1364/oe.446664 2022

  19. [19]

    Single-Mode Sapphire Fiber Temperature Sensor,

    M. Wang et al., “Single-Mode Sapphire Fiber Temperature Sensor,” J. Lightwave Technol., vol. 42, no. 18, pp. 6409–6416, Sep. 2024, doi: 10.1109/JLT.2024.3438108

    work page doi:10.1109/jlt.2024.3438108 2024

  20. [20]

    Method of laser modification of an optical fibre,

    J. Fells, M. Booth, and P. Salter, “Method of laser modification of an optical fibre,” US12321007B2, Jun. 03, 2025

    2025

  21. [21]

    Three-dimensional femtosecond laser nanolithography of crystals,

    A. Ródenas et al., “Three-dimensional femtosecond laser nanolithography of crystals,” Nat. Photonics, vol. 13, no. 2, pp. 105–109, Feb. 2019, doi: 10.1038/s41566-018-0327-9

    work page doi:10.1038/s41566-018-0327-9 2019

  22. [22]

    Monolithic crystalline cladding microstructures for efficient light guiding and beam manipulation in passive and active regimes,

    Y. Jia et al., “Monolithic crystalline cladding microstructures for efficient light guiding and beam manipulation in passive and active regimes,” Sci. Rep., vol. 4, no. 1, p. 5988, Aug. 2014, doi: 10.1038/srep05988

    work page doi:10.1038/srep05988 2014

  23. [23]

    Optical lattice-like cladding waveguides by direct laser writing: fabrication, luminescence, and lasing,

    W. Nie et al., “Optical lattice-like cladding waveguides by direct laser writing: fabrication, luminescence, and lasing,” Opt. Lett., vol. 41, no. 10, p. 2169, May 2016, doi: 10.1364/OL.41.002169

    work page doi:10.1364/ol.41.002169 2016

  24. [24]

    Femtosecond Laser Writing of Optical-Lattice-Like Cladding Structures for Three-Dimensional Waveguide Beam Splitters in LiNbO 3 Crystal,

    J. Lv, Y. Cheng, J. R. Vazquez de Aldana, X. Hao, and F. Chen, “Femtosecond Laser Writing of Optical-Lattice-Like Cladding Structures for Three-Dimensional Waveguide Beam Splitters in LiNbO 3 Crystal,” J. Lightwave Technol., vol. 34, no. 15, pp. 3587– 3591, Aug. 2016, doi: 10.1109/JLT.2016.2573841

    work page doi:10.1109/jlt.2016.2573841 2016

  25. [25]

    Optical-lattice-like waveguide structures in Ti:Sapphire by femtosecond laser inscription for beam splitting,

    Y. Ren et al., “Optical-lattice-like waveguide structures in Ti:Sapphire by femtosecond laser inscription for beam splitting,” Opt. Mater. Express, vol. 7, no. 6, p. 1942, Jun. 2017, doi: 10.1364/OME.7.001942

    work page doi:10.1364/ome.7.001942 1942

  26. [26]

    Sapphire Photonic Crystal Waveguides with Integrated Bragg Grating Structure,

    S. Kefer, G.-L. Roth, J. Zettl, B. Schmauss, and R. Hellmann, “Sapphire Photonic Crystal Waveguides with Integrated Bragg Grating Structure,” Photonics, vol. 9, no. 4, p. 234, Apr. 2022, doi: 10.3390/photonics9040234

    work page doi:10.3390/photonics9040234 2022

  27. [27]

    Photonic Crystal Fibers: A New Class of Optical Waveguides,

    J. Broeng, D. Mogilevstev, S. E. Barkou, and A. Bjarklev, “Photonic Crystal Fibers: A New Class of Optical Waveguides,” Optical Fiber Technology, vol. 5, no. 3, pp. 305–330, Jul. 1999, doi: 10.1006/ofte.1998.0279

    work page doi:10.1006/ofte.1998.0279 1999

  28. [28]

    Guidance varieties in photonic crystal fibers,

    M. Yan and P. Shum, “Guidance varieties in photonic crystal fibers,” Journal of the Optical Society of America B, vol. 23, no. 8, p. 1684, Aug. 2006, doi: 10.1364/JOSAB.23.001684

    work page doi:10.1364/josab.23.001684 2006

  29. [29]

    Properties of photonic crystal fiber and the effective index model,

    J. C. Knight, T. A. Birks, P. St. J. Russell, and J. P. de Sandro, “Properties of photonic crystal fiber and the effective index model,” Journal of the Optical Society of America A, vol. 15, no. 3, p. 748, Mar. 1998, doi: 10.1364/JOSAA.15.000748

    work page doi:10.1364/josaa.15.000748 1998

  30. [30]

    Wavelength- Tunable Dispersion Compensating Photonic Crystal Fibers Suitable for Conventional/Coarse Wavelength Division Multiplexing Systems,

    Jui-Ming Hsu, Che-Wei Yao, and Jian-Zhi Chen, “Wavelength- Tunable Dispersion Compensating Photonic Crystal Fibers Suitable for Conventional/Coarse Wavelength Division Multiplexing Systems,” J. of Lightwave Technol., vol. 33, no. 11, pp. 2240–2245, Jun. 2015, doi: 10.1109/JLT.2014.2380439

    work page doi:10.1109/jlt.2014.2380439 2015

  31. [31]

    Design of single-polarization single-mode photonic crystal fiber at 1.30 and 1.55 /spl mu/m,

    Jian Ju, Wei Jin, and M. S. Demokan, “Design of single-polarization single-mode photonic crystal fiber at 1.30 and 1.55 /spl mu/m,” J. Lightwave Technol., vol. 24, no. 2, pp. 825–830, Feb. 2006, doi: 10.1109/JLT.2005.861942

    work page doi:10.1109/jlt.2005.861942 2006

  32. [32]

    Confinement losses in microstructured optical fibers,

    T. P. White, R. C. McPhedran, C. M. de Sterke, L. C. Botten, and M. J. Steel, “Confinement losses in microstructured optical fibers,” Opt. Lett., vol. 26, no. 21, p. 1660, Nov. 2001, doi: 10.1364/OL.26.001660

    work page doi:10.1364/ol.26.001660 2001

  33. [33]

    Femtosecond laser inscription of depressed cladding single-mode mid-infrared waveguides in sapphire,

    J.-P. Bérubé, J. Lapointe, A. Dupont, M. Bernier, and R. Vallée, “Femtosecond laser inscription of depressed cladding single-mode mid-infrared waveguides in sapphire,” Opt. Lett., vol. 44, no. 1, p. 37, Jan. 2019, doi: 10.1364/ol.44.000037

    work page doi:10.1364/ol.44.000037 2019

  34. [34]

    Femtosecond fiber Bragg grating fabrication with adaptive optics aberration compensation,

    P. S. Salter, M. J. Woolley, S. M. Morris, M. J. Booth, and J. A. J. Fells, “Femtosecond fiber Bragg grating fabrication with adaptive optics aberration compensation,” Opt. Lett., vol. 43, no. 24, p. 5993, Dec. 2018, doi: 10.1364/OL.43.005993

    work page doi:10.1364/ol.43.005993 2018

  35. [35]

    Review and perspective: Sapphire optical fiber cladding development for harsh environment sensing,

    H. Chen, M. Buric, P. R. Ohodnicki, J. Nakano, B. Liu, and B. T. Chorpening, “Review and perspective: Sapphire optical fiber cladding development for harsh environment sensing,” Appl. Phys. Rev., vol. 5, no. 1, p. 11102, Mar. 2018, doi: 10.1063/1.5010184

    work page doi:10.1063/1.5010184 2018

  36. [36]

    2001, MNRAS, 322, 2,

    M. J. Booth, M. A. A. Neil, and T. Wilson, “Aberration correction for confocal imaging in refractive-index- mismatched media,” J. Microsc., vol. 192, no. 2, pp. 90–98, 1998, doi: 10.1111/J.1365- 2818.1998.99999.X

    work page doi:10.1111/j.1365- 1998

  37. [37]

    Exploring the depth range for three-dimensional laser machining with aberration correction,

    P. S. Salter, M. Baum, I. Alexeev, M. Schmidt, and M. J. Booth, “Exploring the depth range for three-dimensional laser machining with aberration correction,” Opt. Express, vol. 22, no. 15, p. 17644, 2014, doi: 10.1364/oe.22.017644

    work page doi:10.1364/oe.22.017644 2014

  38. [38]

    Adaptive optics enhanced direct laser writing of high refractive index gyroid photonic crystals in chalcogenide glass,

    B. P. Cumming, M. D. Turner, G. E. Schröder-Turk, S. Debbarma, B. Luther-Davies, and M. Gu, “Adaptive optics enhanced direct laser writing of high refractive index gyroid photonic crystals in chalcogenide glass,” Opt. Express, Vol. 22, Issue 1, pp. 689-698, vol. 22, no. 1, pp. 689–698, Jan. 2014, doi: 10.1364/OE.22.000689

    work page doi:10.1364/oe.22.000689 2014

  39. [39]

    Extreme environment sensing using femtosecond laser-inscribed fiber bragg gratings,

    S. J. Mihailov et al., “Extreme environment sensing using femtosecond laser-inscribed fiber bragg gratings,” Sensors (Switzerland), vol. 17, no. 12, Dec. 2017, doi: 10.3390/S17122909

    work page doi:10.3390/s17122909 2017

  40. [40]

    Optical properties and electronic structure of amorphous Ge and Si

    H. E. LaBelle and A. I. Mlavsky, “Growth of controlled profile crystals from the melt: Part I - Sapphire filaments,” Mater. Res. Bull., vol. 6, no. 7, pp. 571–579, Jul. 1971, doi: 10.1016/0025- 5408(71)90006-7

    work page doi:10.1016/0025- 1971

  41. [41]

    Anisotropic growth and characterizations of large length-diameter ratio sapphire fibers via laser-heated pedestal growth technique,

    T. Wang et al., “Anisotropic growth and characterizations of large length-diameter ratio sapphire fibers via laser-heated pedestal growth technique,” J. Cryst. Growth, vol. 620, p. 127363, Oct. 2023, doi: 10.1016/j.jcrysgro.2023.127363. Wang and Liu et al. 1 Sapphire Photonic Crystal Fiber Sensor (Supplementary Material) Mohan Wang, Tongyu Liu, Zipei Song...

    work page doi:10.1016/j.jcrysgro.2023.127363 2023