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