Conductive-cooled 2micron laser development for
CO2
and wind measurements
Kohei Mizutani, Toshikazu Itabe, Shoken Ishii National Institute of Information and Communications Technology
Kazuhiro Asai, Atsushi SatoTohoku Institute of Technology
Hirotake FukuokaCentral Research Laboratory, Hamamatsu Photonics K.K.
Takayoshi IshikawaNippon Aleph Co.
Report points of CO2
(WDCGG)
CO2 meas. at Minamitorishima
Anthropogenic emisson 7.2±0.3
Atmospheric CO2
increase
4.1±0.1
Ocean sink
2.2±0.5
Land sink 0.9±0.6
GtC/year
(IPCC FAR) (2000-2005)
Measurements of atmospheric CO2
Uncertainty
GOSAT
Active Sensing
Night high latitudeaerosols
Future Now
50-100mJ at 30pps
2μm
7mJ at 100pps
R=10kmR=10km
NICT Tokyo
R=20km
We need more power!
S/N∝P/√N
Sensing Network ProjectThe atmosphere over the urban area of Tokyo will be observed by Wind Profiler, Doppler lidar,・・
output
7mJ
repetition
100Hz
W.L.
2.012μm
10km
Ground-based wind measurements
5km
Range > 20km is needed.
φ8.0mm
1.3
mm
4
.
0
m
m 4.0
mm
- 7 segments pumping configuration-Composite Tm(4%),Ho(0.4%):YLF Side pump configuration 7-segments heat sink 28 package LD
100mJ oscillator at 2μm and 500mJ amplifier are usable.
0
100
200
300
400
500
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
LD出力(J)
出力
(mJ)
繰返し:10Hz冷媒温度:-85℃
ノーマル出力
Long pulse
Long pulse
Q-sw
10Hz
Expensive not compact
Pumping head for Φ=4mm, L=44mm Tm,Ho:YLF rod12 LD packages
Rod cooling down to -80C in vacuum container
LD controlled to about 20C in vacuum container
Moderate output laser development
Long pulse experimentsMulti-mode Fabry-Perot type Rod temperature ~ –80C
0
25
50
75
100
125
150
175
200
225
250
0.0 0.5 1.0 1.5 2.0
LD光出力(J)
ノー
マル
発振
出力
(mJ)
出力鏡反射率:80%直線状共振器マルチモード
―○―:10Hz―△―:20Hz―×―:30Hz
Output window:80%Multi-mode
Long
pul
se o
utpu
t (m
J)
LD output (J)
OC1 (R_OC=95, 80, 60%)
Power meterM
WIN
YLF
L (f=+5.87m)
100 44
E
真空容器
95 75 100 155
15
Tm,Ho:YLF
Pulse enegyand pulse
width at 20Hz
0
25
50
75
100
125
150
0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6
励起エネルギー(J)
出力
パル
スエ
ネル
ギー
(mJ)
0
100
200
300
400
500
600
QSW
発振
時の
パル
ス幅
(nse
c)
出力鏡反射率:60%繰返し:20Hz
―○―:ノーマル発振―△―:QSW発振―×―:QSW発振時のパルス幅
LD output (J)
Long
pul
se o
utpu
t (m
J)
Long pulseQ-SWPulse width
Output window: 60%Repetition: 20Hz
Puls
e w
idth
(nse
c)
Long pulse
Q-switchWidth
Input: 1.4 J/pulse QSW out :101mJ/pPulse width: 125ns
Output characteristics of Tm,Ho:YLF laser in a ring resonator configuration of 3.86m
Ground-based CO2 DIAL/Wind Doppler Lidar
Fig.2 Block diagram of coherent DIAL.Fig.2 Block diagram of coherent DIAL.Fig.2 Block diagram of coherent DIAL.
Coherent 2-μm Differential Absorption and Wind Lidar (Co2DiaWiL)
Container
2-axes scanner
-0.005
-0.004
-0.003
-0.002
-0.001
0
0.001
0.002
0.003
0.004
0.005
65.0 67.0 69.0 71.0 73.0 75.0
レーザーパルス出射後の時間 (μsec)
バラ
ンス
ドレ
シー
バー
の出
力 (
V) 受信ビート信号 距離範囲:9.75km~11.25km
Beat signal
Spectrum
Example of observation
50mJ at 20Hz
Now operated with 80mJ at 30Hz
-85
-80
-75
-70
95 100 105 110 115
周波数 (MHz)
受信
信号
のPo
wer
Spe
ctru
m(d
B)
-25
-20
-15
-10
送信
信号
のPo
wer
Spe
ctru
m(d
B)
受信光のPower Spectrum
+1.7MHz(LOS方向の風速 +1.7m/sec)
レーザ出力:約50mJレーザパルス幅:約170nsec
送信レーザー光のPower Spectrum
Output power: 50mJPulse width : 170ns
Reference Spectrum
Signal Spectrum
Sign
al P
ower
Spe
ctru
m (d
B)
Ref
eren
ce P
ower
Spe
ctru
m (d
B)
Frequency (MHz)
(LOS wind vel. : +1.7m/sec)
Beat signal
-10
-5
0
5
10
0 5 10 15 20 25 30Range (km)
LOS
velo
city
(m/s
)180秒 (=5400shot)
-10
-5
0
5
10
0 5 10 15 20 25 30Range (km)
LOS
velo
city
(m/s
)
600秒 (=18000shot)
LOS Velocity to Range 80mJ at 30Hz
Velocity measurements up to 23-25km in 10min.
mountain
180s
600s
New laser head for air-borne CO2 DIAL/Wind Doppler lidar Same basic design as the ground based CO2 DIAL
Tm,Ho:YLF rod (Φ=4mm, L=44mm ), (test for Tm,Ho:LLF rod)
Rod cooling down to -80C in vacuum container
12 LD packagesObjective Output 50-80mJ at 30-40Hz
振動試験
New laser head for air-borne CO2 DIAL/Wind Doppler lidar
88.7
OC1 (R_OC=60%)
パワーメータ
M
WIN
Tm:Ho:LuLiF
L (f=+5.87m)
100 44
E
真空容器
81.3 100 69.6100.4
0
25
50
75
100
125
150
175
200
225
250
20 25 30 35 40 45 50 55 60
LD駆動電流 (A)
ノー
マル
発振
出力
(m
J)
出力鏡反射率:60%直線状共振器マルチモード励起パルス幅:1msチラー設定 ロッド:-85℃ LD :+16℃
―○―:10Hz―△―:20Hz―×―:30Hz
Tm,Ho:LLF rod
Long pulse experimentsMulti-mode Fabry-Perot type Rod temperature ~ –80C
LD current (A)
New laser head for air-borne CO2 DIAL/Wind Doppler lidar
Tm,Ho:YLF rod Tm,Ho:LLF rodLong
pul
se o
utpu
t (m
J)
400mm66
0mm
New test laser for air-borne CO2 DIAL/Wind Doppler lidar
Concept and simulation studies for 2micron Integrated path differential absorption (IPDA) lidar
Name concept on/off(mJ) repetition Telescope Dia.FACTS 2micron double wing 75/25 10Hz 1m
Direct detection
Ehret et al. 2micron wing 80/70 50Hz 1.5m Direct detection Appl.Phys.B90,593(2008)
NICT Conductive-cooled ≦100mJ ≦30Hz (limit of LD driver) 2micron laser Oscillator 80mJ at 50Hz may be possible
NICT Conductive-cooled ~500mJ 10Hz 2micron laser Amplifier
NICT Conductive-cooled 2micron laser seems to be fit to the Direct detection IPDA lidar.
laser Refle ction
ConclusionsWe have developed a ground-based DIAL/Wind Doppler lidar(Co2DiaWiL) on an optical table with a 2 μm conductive-cooled Tm,Ho:YLF laser of 50-80mJ output at 30Hz.
The output of the slave laser will reach to 100mJ at 30Hz.
Laser amplifier of 500mJ level is available.
A compact mobile CO2 DIAL/WIND system will be developed and used for the air-borne and ground-based observations. (Validation experiments of GOSAT )
These output power may be large enough for some kinds of space-borne CO2 DIAL and Wind Doppler lidar.
The conductive-cooled lasers could be applicable to space-borne 2μm DIAL and Wind lidar for global CO2 and wind measurements