Dr. Stephen Ho Profile

Dr. Stephen Ho

Research Scientist at Univ of Toronto

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Publications (10)

Proceedings Article | 5 March 2022 Presentation

Fiber-to-silicon photonics interposer for high-density vertical coupling through laser structured mirror-waveguide circuits

Gligor Djogo, Amir Rahimnouri, Jianzhao Li, Stephen Ho, Peter Herman

Proceedings Volume PC12007, PC120070H (2022) https://doi.org/10.1117/12.2609088

KEYWORDS: Waveguides, Photonics, Structured optical fibers, Optical fibers, Optical circuits, Mirrors, Glasses, Femtosecond phenomena, Chemical elements, Wet etching

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Proceedings Article | 7 March 2021 Presentation

Femtosecond laser micro-structuring of air-disk mirrors in glass for out-of-plane waveguide coupling in silicon photonic packaging

Gligor Djogo, Amir Rahimnouri, Stephen Ho, Jianzhao Li, Peter Herman

Proceedings Volume 11676, 116760S (2021) https://doi.org/10.1117/12.2581679

KEYWORDS: Mirrors, Waveguides, Glasses, Packaging, Silicon photonics, Femtosecond phenomena, Reflection, Etching, Wet etching, Waveguide lasers

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Proceedings Article | 21 April 2017 Presentation

Manipulating femtosecond laser interactions in bulk glass and thin-film with spatial light modulation (Conference Presentation)

Ehsan Alimohammadian, Stephen Ho, Erden Ertorer, Sebastian Gherghe, Jianzhao Li, Peter Herman

Proceedings Volume 10094, 100940Z (2017) https://doi.org/10.1117/12.2255877

KEYWORDS: Modulation, Spatial light modulators, Thin films, Femtosecond phenomena, Glasses, Beam shaping, Waveguides, Optical tracking, Spherical lenses, Plasma

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Spatial Light Modulators (SLM) are emerging as a power tool for laser beam shaping whereby digitally addressed phase shifts can impose computer-generated hologram patterns on incoming laser light. SLM provide several additional advantages with ultrashort-pulsed lasers in controlling the shape of both surface and internal interactions with materials. Inside transparent materials, nonlinear optical effects can confine strong absorption only to the focal volume, extend dissipation over long filament tracks, or reach below diffraction-limited spot sizes. Hence, SLM beam shaping has been widely adopted for laser material processing applications that include parallel structuring, filamentation, fiber Bragg grating formation and optical aberration correction.

This paper reports on a range of SLM applications we have studied in femtosecond processing of transparent glasses and thin films. Laser phase-fronts were tailored by the SLM to compensate for spherical surface aberration, and to further address the nonlinear interactions that interplay between Kerr-lens self-focusing and plasma defocusing effects over shallow and deep focusing inside the glass. Limits of strong and weak focusing were examined around the respective formation of low-loss optical waveguides and long uniform filament tracks. Further, we have employed the SLM for beam patterning inside thin film, exploring the limits of phase noise, resolution and fringe contrast during interferometric intra-film structuring.

Femtosecond laser pulses of 200 fs pulse duration and 515 nm wavelength were shaped by a phase-only LCOS-SLM (Hamamatsu X10468-04). By imposing radial phase profiles, axicon, grating and beam splitting gratings, volume shape control of filament diameter, length, and uniformity as well as simultaneous formation of multiple filaments has been demonstrated. Similarly, competing effects of spherical surface aberration, self-focusing, and plasma de-focusing were studied and delineated to enable formation of low-loss optical waveguides over shallow and deep focusing conditions.

Lastly, SLM beam shaping has been successfully extended to interferometric processing inside thin transparent film, enabling the arbitrary formation of uniform or non-uniform, symmetric or asymmetric patterns of flexible shape on nano-scale dimensions without phase-noise degradation by the SLM patterning. We present quantized structuring of thin films by a single laser pulse, demonstrating λ/2nfilm layer ejection control, blister formation, nano-cavities, and film colouring. Closed intra-film nanochannels with high aspect ratio (20:1) have been formed inside 3.5 um thick silica, opening new prospects for sub-cellular studies and lab-in-film concepts that integrate on CMOS silicon technologies.

Proceedings Article | 21 April 2017 Presentation

Holographic tracking of quantized intra-film segments during interferometric laser processing of SiOx thin films (Conference Presentation)

Stephen Ho, Matthias Domke, Heinz Huber, Peter Herman

Proceedings Volume 10094, 100941B (2017) https://doi.org/10.1117/12.2257034

KEYWORDS: Holography, Thin films, Interferometry, Femtosecond phenomena, Holographic interferometry, Laser processing, Dielectrics, Nanostructuring, Plasma, Refractive index

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Proceedings Article | 19 April 2017 Paper

Femtosecond laser direct-write of optofluidics in polymer-coated optical fiber

Kevin A. Joseph, Moez Haque, Stephen Ho, J. Stewart Aitchison, Peter Herman

Proceedings Volume 10094, 1009414 (2017) https://doi.org/10.1117/12.2256996

KEYWORDS: Polymers, Optical fibers, Microfluidics, Waveguides, Femtosecond phenomena, Cladding, Fiber lasers, Fiber Bragg gratings, Structured optical fibers, Silica

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Proceedings Article | 15 March 2017 Presentation + Paper

Control of femtosecond laser interference ejection with angle and polarisation

David Roper, Stephen Ho, Moez Haque, Peter Herman

Proceedings Volume 10094, 100940T (2017) https://doi.org/10.1117/12.2256995

KEYWORDS: Femtosecond phenomena, Laser processing, Thin films, Interferometry, Interfaces, Visibility, Polarization, Silicon, Reflection, Silicon films

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Proceedings Article | 12 April 2005 Paper

Thermal heating effects in writing optical waveguides with 0.1 - 5 MHz repetition rate

Shane Eaton, Fumiyo Yoshino, Lawrence Shah, Alan Arai, Haibin Zhang, Stephen Ho, Peter Herman

Proceedings Volume 5713, (2005) https://doi.org/10.1117/12.591058

KEYWORDS: Waveguides, Silica, Thermal effects, Glasses, Borosilicate glass, Ultrafast lasers, Optical microscopes, Signal attenuation, Refractive index, Pulsed laser operation

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Proceedings Article | 12 April 2005 Paper

F2-laser microwelding of optical fibers and glass substrates

Stephen Ho, J. Aitchison, Peter Herman

Proceedings Volume 5713, (2005) https://doi.org/10.1117/12.591130

KEYWORDS: Glasses, Laser welding, Silica, Optical fibers, Laser ablation, Absorption, Fiber lasers, Interfaces, Laser processing, Telecommunications

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Proceedings Article | 21 March 2005 Paper

MHz-rate ultrafast fiber laser for writing of optical waveguides in silica glasses

Lawrence Shah, Fumiyo Yoshino, Alan Arai, Shane Eaton, Haibin Zhang, Stephen Ho, Peter Herman

Proceedings Volume 5714, (2005) https://doi.org/10.1117/12.590850

KEYWORDS: Waveguides, Silica, Glasses, Femtosecond phenomena, Laser processing, Microscopes, Borosilicate glass, Oscillators, Wave propagation, Laser systems engineering

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Proceedings Article | 8 December 2004 Paper

F2-laser microfabrication for integrating optical circuits with microfluidic biochips

Stephen Ho, J. Aitchison, Shane Eaton, Peter Herman, Jianzhao Li

Proceedings Volume 5591, (2004) https://doi.org/10.1117/12.571338

KEYWORDS: Waveguides, Microfluidics, Glasses, Silica, Lab on a chip, Refractive index, Sensors, Optical spheres, Laser ablation, Wave propagation

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Showing 5 of 10 publications

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