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Lasing wavelength in dielectric distributed-feedback lasers with a distributed phase shift
KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
KTH.
KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.ORCID iD: 0000-0001-7688-1367
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2019 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Distributed-feedback waveguide lasers based on Bragg-grating resonators generate ultranarrow-linewidth emission. Oscillation at the center of the reflection band ensures maximum reflectivity, hence minimum laser linewidth. The required μ/2 phase shift is often introduced by a distributed change in effective refractive index, e.g. by adiabatically widening the waveguide. Despite careful design and fabrication, the experimentally observed resonance wavelength deviates, thereby placing the resonance and laser emission at a position with lower reflectivity inside the reflection band. This effect is usually incorrectly attributed to fabrication errors. Here we show theoretically and experimentally that the decay of light intensity during propagation from the phase-shift center into both sides of the Bragg grating due to (i) reflection by the periodic grating and (ii) the adiabatic refractive-index change causes an incomplete accumulation of designed phase shift, thereby systematically shifting the resonance to a shorter wavelength. Calculations are performed based on the characteristic-matrix approach. Experimental studies are carried out in a distributed-feedback channel-waveguide resonator in amorphous Al2O3 on silicon with a distributed phase shift introduced by adiabatic widening of the waveguide according to a sin2 function. Calculations and experiments show good agreement. Considering in the design the overlap integral between distributed phase shift and light intensity provides the desired performance.

Place, publisher, year, edition, pages
2019. Vol. 10896
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-251676DOI: 10.1117/12.2514805ISI: 000483062600027Scopus ID: 2-s2.0-85068323261OAI: oai:DiVA.org:kth-251676DiVA, id: diva2:1316432
Conference
SPIE Photonics West, 02 - 07 February 2019, San Francisco - USA
Note

QC 20190819

Available from: 2019-05-17 Created: 2019-05-17 Last updated: 2019-12-20Bibliographically approved

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Kores, Cristine CalilIsmail, NurLaurell, FredrikPollnau, Markus

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