General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.

Users may download and print one copy of any publication from the public portal for the purpose of private study or research.

You may not further distribute the material or use it for any profit-making activity or commercial gain

You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Downloaded from orbit.dtu.dk on: Jul 10, 2021

Systematically Varying the Active Material Volume in a Photonic Crystal Nanolaser

Mathiesen, Kristoffer Skaftved; Sakanas, Aurimas; Semenova, Elizaveta; Yvind, Kresten; Mørk, Jesper

Published in:The European Conference on Lasers and Electro-Optics 2019

Publication date:2019

Document VersionPublisher's PDF, also known as Version of record

Link back to DTU Orbit

Citation (APA):Mathiesen, K. S., Sakanas, A., Semenova, E., Yvind, K., & Mørk, J. (2019). Systematically Varying the ActiveMaterial Volume in a Photonic Crystal Nanolaser. In The European Conference on Lasers and Electro-Optics2019 [Paper cb_p_20] Optical Society of America.

https://orbit.dtu.dk/en/publications/8848d10f-8e93-4fdc-a55b-1624ba8fded4

SYSTEMATICALLY VARYING THEACTIVE MATERIAL VOLUME IN APHOTONIC CRYSTAL NANOLASER

K. S. MATHIESEN, A. SAKANAS, E. SEMENOVA, K. YVIND, J. MØRK

INTRODUCTIONUsing light for data transmission promises higher speeds than tradi-tional transmission through copper wires [1]. The bottleneck for in-troducing optical components in various transmission is energy con-sumption and ultimately price. Today data transmission throughmetallic interconnects on chip use more than 50% of the total powerconsumption [2] and optics could be faster and cheaper. Photoniccrystal lasers have already shown great promise [3]. Here we presentan investigation of laser characteristics where the extent of the gainmaterial is varied while the photonic crystal cavity is kept constant.This systematic variation gives control of the total gain material in thecavity as well as confinement factor and allows for systematic inves-tigations, e.g. of the role of slow-light effects on the threshold gain.

DESIGN AND FABRICATIONA photonic crystal line defectcavity fabricated around a selec-tively etched gain material al-low for a very compact struc-ture. The slow-light phenomenaoccuring in line defect photoniccrystal waveguides also add en-hanced gain [4] and having BHembedded in an InP membraneprovides good thermal operation[5]. The length of the active ma-terial region within the photoniccrystal cavity is varied in stepsa one photonic crystal period, a.This variation is done in a nor-mal L7 cavitiy as well as an op-timized cavity where holes areshifted to increase Q-factor [6, 7].

Optimized L7 cavity with shifted holes.

The BH is etched to highlight alignment.

Unetched QWs remain for long BH.

REFERENCES[1] D. Miller Device requirements for optical interconnects to silicon chips. Proc. IEEE,

97, 1166 (2009)[2] N. Magen et al. Interconnect-power dissipation in a microprocessor. Proceedings

of System Level Interconnect Prediction, 1-2, (2004)[3] K. Takeda et al. Few-fJ/bit data transmissions using directly modulated lambda-

scale embedded active region photonic-crystal lasers. Nature Photonics, 7, 569(2013)

[4] S. Ek et al. Slow-light-enhanced gain in active photonic crystal waveguides. NatureCommunications, 5, 5039 (2014)

[5] W. Xue et al. Thermal analysis of line-defect photonic crystal lasers. Opt. Express,23, 18277 (2015)

[6] Y. Akahane et al. High-Q photonic nanocavity in a two-dimensional photonic crys-tal. Nature, 425, 944 (2003)

[7] K. Maeno et al. Analysis of high-Q photonic crystal L3 nanocavities designed byvisualization of the leaky components. Opt. Express, 25, 367 (2017)

[8] W. Xue et al. Threshold Characteristics of Slow-Light Photonic Crystal Lasers.Phys. Rev. Lett, 116, 063901, (2016)

EQUIVALENT PASSIVE CAVITIESThe photonic crystals design isinvestigated in the FDTD simu-lation software Lumerical to op-timize resonance wavelengths,Q-factors and mode volumesbefore fabrication. Simulationsof the equivalent passive cavi-ties highlight how the resonanceshifts as the size of the gain re-gion is increased, correspondingto a higher effective refractive in-dex in the cavity region.

Simulations with varying BH length.

EXPERIMENTAL SETUPThe sample is pumped from thetop with a 300 mW CW laser@1480 nm. Scattered light is thencollected via the same objectiveand split from the pump by aWDM. This allows for collectionof input-output curves from dif-ferent lasers to be obtained. Thecurves can be fitted to a laser rateequation model and parameterscan be extracted [8], while thethreshold powers can be readilyobtained. Measurement setup.

EXPERIMENTAL RESULTSThe resonance wavelengths obtained from experiments redshifts asthe BH is increased and agree well with simulations. From the input-output curves it can be seen that the sample with BH smaller than twoperiods doesn’t lase.

Resonance wavelength of lasing modescompared to simulation.

Input-output curves for different BHlengths.

Threshold powers have also been extracted and the maximum outputpower above threshold for the different BH lengths but no clear trendappears.

Thresholds extracted for various BHlengths.

Output powers for an input power of 57mW.

OUTLOOK• Further investigate the

threshold powers.• Fit data to a rate equation

model, to extract laser pa-rameters.

• Fabricate new sample withsmaller increments in theBH around 0a-2a wherethe transition from LED tolaser behaviour changes.