MidInfrared Light Sources Based on Difference Frequency Generation in DirectBonded PeriodicallyPoled

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Mid-Infrared Light Sources Based on Difference
Frequency Generationin Direct-Bonded
Periodically-Poled LiNbO3 Ridge Waveguides
MIOMD-?, Lancaster, Sep. 11-14
H. Suzuki, O. Tadanaga, T. Yanagawa, Y.
Nishida H. Miyazawa, K. Magari and M. Asobe NTT
Photonics Laboratories NTT Corporation
(hiroyuki_at_aecl.ntt.co.jp)

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Outline

• Background
• Key device High-efficiency PPLN waveguides
• Application to visible laser sources
• Characteristics of mid-IR DFG light sources in
  the 2-3mm regions
• Demonstration of gas absorption measurements
• Future plan

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High-efficiency wavelength converter for WDM
applications
Device structure
0-dB DWDM signal conversion
40Gb/sx8ch conversion by multi-PPLN WC
Telecom applications ? Non-telecom applications
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Construction of laser light sources
Telecom LD1

l3 generation by SFG or DFG in PPLN WG
Telecom LD2
PPLN WG
Desired laser light generation from selected?1
?2 Sum-frequency generation (SFG) _at_
visible Difference-frequency generation (DFG) _at_
mid-IR
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560-590 nm light sourcesusing sum-frequency
generation

Output wavelength 560nm 0.98mm1.3mm 590nm
1.06mm1.3mm

• Output power
• gt10mW for CW
• gt5mW for direct modulation
• Direct modulation capability
• Low noise

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Mid-infrared DFG light source based on PPLN
waveguide

• Telecom LD pumped
• mid-IR light generation
• between 2 and 5 mm
• gtRT CW operation
• Widely tunable
• _at_ 2.3-mm range

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Absorption intensity of various gases
Target wavelengths
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Direct bonded ridge waveguide
Zn-doped or non-doped LN substrate
Diamond blade
Electrical poling
Polarization
Direct bonding
Bonded LN/LT wafer
LT or Mg-doped LN substrate
lt10 mm
Lapping and polishing
Waveguide fabrication using dicing saw
Photograph of waveguide cross-section
High damage resistance Long-term
reliability High conversion efficiency
Precise design
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DFG characteristics of3-mm band waveguide
DFG tuning curve
L 28.4 mm L50 mm RT
Pump NdYLF 10 mW Signal Tunable LD 1 mW
Conversion efficiency 40 /W Output 0.26-mW
with 11-mW pump and 66-mW signal
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CH4 (_at_ 3.3 mm) detection setup
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CH4 absorption spectrum
CH4 gas cell 10 Torr, 20cm (CaF2 windows)
Reference cell 10-5 Torr, 20cm (CaF2 windows)
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Broad-band phase-matching_at_ 2.3 mm
lp 0.94 mm Wide tuning range _at_ 2.3 mm
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Simulated DFG characteristicsin a 5 cm-long bulk
sample
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DFG tuning curve
DFG characteristics of fabricated 2mm-band
waveguide
Signal power vs Output power
L 25.60 mm L50 mm RT
3-dB bandwidth _at_ RT 100 nm Conversion
efficiency 100 /W Output gt0.4 mW
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CO (_at_ 2.4 mm) detection setup
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CO isotopomer absorption spectrum
12CO / buffer gas cell 300 Torr, 20cm
(anhydros SiO2 windows) 13CO / buffer gas
cell 300 Torr, 20cm (anhydros SiO2 windows)
12CO (100Torr)
13CO (100Torr)
Reference gas cell 300 Torr, 40cm
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CO ro-vibration absorption spectra
12CO (100 Torr, 20cm)
13CO (100 Torr, 20cm)
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Assignment of 12CO ro-vibration absorption lines
P-branch
R-branch
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Signal bandwidth vs Pump wavelength
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ppm-level CO2 detection in air _at_ 2.7 mm
4 ppm
Multi-pass cell Pump laser _at_ 0.98 mm
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Mid-IR PPLN waveguide module
PPLN waveguide module
PPLN waveguide
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Summary

• Laser diode pumped mid-IR light sources
• using DFG in direct bonded PPLN waveguide.
• Mid-IR light generated in the 2- and 3-mm
  regions.
• Conversion efficiency 40100 /W.
• Output mW level
• Absorption measurements demonstrated
• for CH4, CO isotomomers and CO2.
• Mid-IR PPLN waveguide being developed.