Flexible Compact InGaAsP Microdisk Lasers on a PFlexible Compact InGaAsP Microdisk Lasers on a Polydimethylsiloxane (PDMS) Substrateolydimethylsiloxane (PDMS) Substrate

Kung-Shu HsuKung-Shu Hsu1,2 1,2 ((徐功書徐功書 ), Yao-Chen Wang), Yao-Chen Wang1,31,3 ( (王耀振王耀振 ), Yi-Chun Yang), Yi-Chun Yang11 ( (楊怡君楊怡君 ), Shih-Kuo Tsai), Shih-Kuo Tsai1,31,3 ( (蔡世國蔡世國 ), Zi-Chang Chang), Zi-Chang Chang1,31,3 ( (張子倉張子倉 ), ), Yu-Chen LiuYu-Chen Liu1,31,3 ( (劉育辰劉育辰 ), M. C. Wu), M. C. Wu33 ( (吳孟奇吳孟奇 ) and M. H. Shih) and M. H. Shih1,21,2 ( (施閔雄施閔雄 ))

1Research Center for Applied Science (RCAS), Academia Sinica, Taiwan. 2Department of Photonics, National Chiao Tung University, Taiwan.

3Department of Electrical Engineering, National Tsing Hua University , Taiwan. Address: 128 Sec.2, Academia Rd., Nankang, Taipei 11529, Taiwan

Phone : 03-5712121 ext.59470, Fax : 03-5745233 Email : mhshih@gate.sinica.edu.tw

Abstract : Compact microdisk cavities were fabricated on a polydimethylsiloxane substrate. The lasing of the flexible compact cavity was achieved with a low threshold power. The whispering-gallery mode of the microdisk was also characterized with finite-difference time-domain simulation. The curvature dependence in output power and threshold was also demonstrated by bending the microdisk cavity.

Introduction

Fabrication Process

Measurement

The microdisk lasers were optically-pumped at room temperature by using an 850 nm wavelength diode laser at normal incidence with a 1.5% duty cycle and a 30 ns pulse width.

Summary

The compact size, flexible microdisk lasers on a PDMS substrate had been demonstrated. The lasing near 1550 nm wavelength was achieved with a low threshold power of 0.55 mW. The curvature dependence in lasing power and threshold were also characterized with the small bending of the cavities. This novel flexible microdisk laser can benefit to compact light source or sensor in the future photonic integrated systems.

(a) The SEM image of an array of fabricated disks on the PDMS substrate with varied diameters of 1.80, 2.85, 3.80 and 4.75 μm (b) The magnified SEM image of a microdisk laser with 4.75 μm diameter

Measurement results of a microdisk cavity with 4.75μm diameter

150015201540156015801600162016400

10

20

30

40

50

60

70

80

10-4

10-3

10-2

10-1

100

101

102

Ou

tpu

t P

ow

er

(pW

)

Wavelength (nm)

Mo

nito

r V

alu

e (

a.u

.)

L=1572.6nm

Q=11000 Q=1400

L=1580.1nm

Bonded to PDMS

substrate

RIE

E-beam lithography

ICP

InP

InGaAsPSiNx

PMMA

InP

InGaAsPSiNx

PMMA

InP

InGaAsPSiNx

InP

InGaAsPSiNx

PDMSPDMS

Removed InP

Semiconductor Microdisk Cavities • Compact size • Low threshold power• High quality factor (Q)

Polymer Photonic Devices • Application flexibility • Low cost • Special spectral properties

To demonstrate the semiconductor microdisk lasers on the flexible polymer substrate

Lasing Spectrum

1560 1580 16000.0

0.5

1.0

Ou

tpu

t (a

.u.)

Wavelength (nm)

L = 1577.6 nm

L-L Curve

0.0 0.5 1.0 1.50

20

40

60

Ou

tpu

t P

ow

er

(pw

)

Incident Pumped Power (mW)

Incident threshold~ 0.55 mW

2 4 6 8 100.0

0.5

1.0

1.5

2.0

2.5

3.0

Th

resh

old

Po

we

r (m

W)

Microdisk Diameter (m)

0.00 0.01 0.02 0.03 0.04 0.05 0.0640

50

60

70

80

Pea

k P

ower

(pW

)

Curvature (1/mm)

(c) The lasing threshold power varied with different microdisk diameter(d) Comparison of 3D FDTD simulation and measurement spectrum (e) The top view of HZ mode profile from the 3D FDTD simulation

The structure was bended along a diameter of the disk with a small curvature (1/R)

Lasing data of a bent microdisk cavity with 4.75μm diameter

The SEM images of the microdisk lasers

μ- disk

R

PDMS

(a) (b)

(c)

(d) (e)

PDMS

240 nmμ- disk

InGaAsP

4 × QW