Self-Guided Operation of Green-Pumped Singly Resonant CW OPO based on Bulk MgO:PPLN

 

In-ho Bae,1 Han Seb Moon,1 Sebastian Zaske,2 Christoph Becher,2 Seung Kwan Kim,3 Seung-Nam Park,3 and Dong-Hoon Lee3,*

 

1Department of Physics, Pusan National University, Busan 609-735, Rep. Korea2Universität des Saarlandes, Fachrichtung 7.3 (Technische Physik), 66123 Saarbrücken, Germany

3Division of Physical Metrology, Korea Research Institute of Standards and Science (KRISS), Daejeon 305-340, Rep. Korea 

* Email: dh.lee@kriss.re.kr

Contents• Introduction

• Singly resonant CW OPO setup

• CW OPO Cavity degin

• Experimental results– Wavelength tuning curve

– Thermal wave-guide effect

– Output power characteristics

– Continuous tuning range

– Thermal absorption time

– Spatial mode profile

– Pump mode profile

• Summary

IntroductionContinuous-wave (CW) optical parametric oscillators (OPOs) based on quasi-phase-matching (QPM)

broad wavelength coverage wide single-frequency tuning rangecorrelations between the signal and idler output beams

thermal lensing and de-phasing

limitation of parametric efficiency, spatial mode quality, spectral tuning property, and stability of CW OPOs

Nonlinear crystal

Cavity design

Singly resonant OPO setupHR : high reflectivity HWP : half-wave plateISO : isolator A : apertureOSA : optical spectrum analyzer BD : beam dump

MgO: PPLN

OvenTranslator

XY stagePolling period Λ7.2 μm, 7.4 μm, 7.6 μm, 7.8 μm

Pump : 532 nm

Signal : 770~890 nm

Idler : 1330~1680 nm

Wavelength tuning curve

Signal : 770~890 nm

Idler : 1330~1680 nm

40 50 60 70 80 90 100 110750

800

850

900

1300

1400

1500

1600

1700

1800

7.8 m

7.6 m

7.4 m

7.8 m

7.6 m

7.4 m

7.2 m

Ou

tpu

t w

ave

len

gth

(n

m)

Temperature (oC)

7.2 m

We fitted experimental results by using Sellmeier equations for 5% MgO-doped congruent PPLN in Ref. [1].

[1] Gayer et. al. Appl. Phys. B 91, 343–348.

Thermal wave-guide effect

)arccos(1

2 21,, ggnm

qnL

cnmq

▶ Resonance frequency of the TEMnmq Mode

▶ Transverse mode spacing

22

11 1&1

R

Lg

R

Lg

▶ Resonator g parameters & Stability condition

10 21 gg

Laser Resonator Stability Diagram

nL

cggnmq

2

)arccos( 21,,

R = 50 mm, limited cavity length : 100 mmL > 100 mm unstable cavity

In our case, unstable cavity is above 122 mm.

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

Sign

al o

utpu

t (W

)

Pump power (W)

s118 s120.5 s122 s126 s129 s132 s135 s138

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

Idle

r O

utpu

t (W

)

Pump power (W)

i118 i120.5 i122 i126 i129 i132 i135 i138

Output power characteristics

0 200 400 600 800 1000

Out

put p

ower

(ar

b. u

nits

)

Frequency (MHz)

Signal Idler reflection PZT scan

600 MHz

98 mm

Continuous tuning range

0 100 200 300 400 500 600 700 800 900 1000

Out

put p

ower

(ar

b. u

nits

)

Frequency (MHz)

Signal Idler reflection PZT scan

600 MHz

0 200 400 600 800 1000

800 MHz

Out

put p

ower

(ar

b. u

nits

)

Frequency (MHz)

Signal Idler reflection PZT scan

500 MHz

109.4 mm

115.4 mm

Thermal absorption time

-10 0 10 20 30

Sign

al a

mpl

itud

e (a

rb. u

nits

)

Time (ms)-20 -10 0 10 20 30

Sign

al a

mpl

itud

e (a

rb. u

nits

)Time (ms)

Leff 93.4 mm

Leff 115.4 mm

Spatial mode profile

Leff 98 mm Leff 109.4 mm

Leff 115.4 mm

Pump mode profilebefore afte

r

Summary

We operated Self-Guided singly resonant CW OPOs that was assisted by thermal wave guide effect.

We got 400 ~ 600 MHz and 600 ~ 800 MHz for continuous tuning range under the stable and unstable cavity condition, respectively.

The spatial mode of the CW OPOs were improved by thermal effect in unstable cavity and the Gaussian mode profile was achieve at the maximum cavity length.

In the near future, CW – OPOs with unstable cavity method will be used to find atomic transition spectrum though optimization and stabilization of continuous tuning range.