Development of the interferometer (1)— Development steps of the TAMA300 interferometer —• TAMA300 interferometer is developed step by step....
Data acquisition system
Recycling mirror

10W laser

10W laser+ Mode cleaner
Mode cleaner
Power-recycled interferometer
300m Fabry-Perot-Michelson interferometerwith 10W laser source and mode cleaner
300marm cavity

300m Fabry-PerotMichelson interferometer

1998.5

Now under development.
1999.7

1999.2

1

1999.8

1999.111999.3

Development of the interferometer (2)— First observation phase (Phase I) —• First observation phase of TAMA300 (Phase I).
· Start in August, 1999.
· Operate almost the whole interferometer.
· 10 W laser source with 10 m mode cleaner.
· Main interferometer with 300 m arm cavities.
· Without power recycling.
· Sensitivity — h ∼ 3 × 10−20 .
√−19m/ Hz.
⇒ Displacement noise < 5 × 10√−6Hz/ Hz.
Laser frequency noise < 1 × 10⇓
• Developing the interferometer.
— The interferometer is operated with the final configuration.
2

Development of the interferometer (3)— TAMA300 interferometer for Phase I —Fabry-Perot-Michelson interferometerwith an arm length of 300 m
EM2300 m arm cavity(NS arm)

Injection-locked
10 W laser
20 MHzMirroralignment
controlloopδL yDifferential motion
control loop (δL-)

FM2Mixer

Injection locking
control loop

10 m Mode cleaner

Mixer

QPD
Mixer

300 m arm cavity (WE arm)

PD

Fiber LDPO2YAG

IM

OM

PD

BS

FM1

FI

EOM

EOM
VCM

PO1

LD pumped
10 W laser
15.235 MHz

PD

20 MHz

NPRO
700 mWMixer

10 mringcavity

Mirror alignment
control loop

Interference fringe
control loop (δl-)

Mixer
EOM

EOM

PD

12 MHz

Mixer

Mixer

QPD

Mixer

PD

PD

Mixer

δL x

EM
SUM

Laser frequency
stabilization loop

30 kHzGravitational wave signal (δL-)
MC mass loop
SUM

Feed around loop

Common motion
control loop (δL+)

3EM1

10-W laser source (1)— Features —• Injection-locked Nd:YAG laser.
· Output power of 10 W.
· Master laser

Injection-locked 10 W laser
20 MHzInjection locking
control loop

· LD-pumped Nd:YAG laser (700 mW).

PD

Fiber LD

· Frequency-controlled with
Thermal control, PZT, External EOM.

YAG

· Slave laser

VCM

10W laser beam

LD pumped
10 W laser· Fiber LD-pumped ring laser.
· Injection-locked to the master laserwith a VCM (Voice Coil Motor).

20 MHzNPRO700 mW
EOM· Error signal is extractedusing 20 MHz phase modulation.

· Intensity stabilization

SUM· Controlled with an external EOM.
Laser frequency
control signal

4MixerEOM

10-W laser source (2)— Intensity stabilization —• Intensity noise is stabilized using an EOM.
√−81/ Hz.
— stabilized to 2 × 10–2

10–3

10–4

10–5

10–6

10–7

10–8

Intensity noise [1/Hz–1/2]

10Free run
Monitor signal
Error signal

Shot–noise level–910 –1
10010101210
10Frequency [Hz]53410105

10-m mode cleaner (1)— Features —• 10-m ring cavity.
Injection-locked
10 W laser· Three mirrors— Independently suspended(double pendulum).

10 m Mode cleaner

Injection locking
control loop

· Finesse — 1,700.

IM· Transmissivity — 54%.

EOMEOM

LD pumped
10 W laser• Length control

20 MHz

NPRO
700 mW· Error signal —extracted using 12 MHz phase modulation,
fed back to to laser source.

• Transmission of
the modulation sidebands.

15.235 MHzMixer

12 MHzEM
30 kHz· FSR = Modulation freq. (15.235 MHz).

610 mringcavityMixer

SUM· Error signal— extracted using additional modulation.

PDLaser frequency
stabilization loop

OM

10-m mode cleaner (2)— Frequency stabilization —Frequency noise [Hz/Hz–1/2]• Laser frequency noise— pre-stabilized using the 10-m mode cleaner.
√−4Hz/ Hz.
→ stabilized to 5 × 10
710
610
510
410
3102
10
1
10
0
10–1
10–2
10–3
10–4
10 –1
10Free run
Error signal (MC loop)

10010

1210
10Frequency [Hz]7310410510-m mode cleaner (2)— Transmission of the modulation sidebands —• Phase modulator
for the control of the main interferometer
10 m Mode cleaner· Placed before the MC.
→ reduce the wave-front distortion.
· Modulation frequency (νmod)— equal to the FSR of the MC (νFSR).
⇓IMEOM

15.235 MHz

PD
Mixer

· Modulation sidebands pass through the MC.

10 mringcavity

12 MHz· Cause excess noise
without fine adjustment of νmod.

EMLaser frequency
control

8EOMOM10-m mode cleaner (3)— Excess noise —Excess noise [V/Hz–1/2]• Adjust the modulation freq. equal to the FSR of the MC.
(the difference — below 10 Hz)

10–3

10–4

Excess noise (Q–phase)

Shot noise

10–510–6

Detection system noise

10–1

10010121010
Frequency [Hz]3

• Excess noise is below the shot noise level (30 mA).
9104105300-m arm cavity (1)— Features —• 300-m Fabry-Perot arm cavities· Finesse — 516.
· Cut-off frequency — 480.
· Alignment control system (Wave-front sensing scheme).
WE–arm cavity response

NS–arm cavity response

121210Abs. [V/m]Abs. [V/m]101110101091010310110410

Phase [deg]Phase [deg]21000
fc = 493 Hz
1101010910
110–100

1110210310
Frequency [Hz]431043100–100

fc = 485 Hz

101010100

1102

1021010Frequency [Hz]4

300-m arm cavity (2)— Alignment control —• Operated stably with the alignment control system.
Four degrees of freedom are controlled for each arm cavity.

Transmitted light power [V]7654yaw cantrol on

32pitch control on

10010203040Time [sec.]

115060300-m arm cavity (3)— Long term operation —• One arm cavity — operated about 4 days without unlock.
· Laser source — 700 mW NPRO.
· With alignment control.

Transmitted light power [V]765432100

10 20 30 40 50 60 70 80 90 100
Time [hour]
12Main interferometer with the 300-m arm cavities (1)— Features —• Michelson interferometer withthe 300-m Fabry-Perot arm cavities.

Fabry-Perot-Michelson interferometerwith an arm length of 300 m· Finesse — 516.

EM2· Cut-off frequency — 480.

• Controlled withthe frontal modulation scheme.

δL yDifferential motion
control loop (δL-)

FM2
Mixer

· δL− signal — fed back to the front mirrors (diff.).

QPD
Mixer

300 m arm cavity (WE arm)

· δl− signal — fed back to the beam splitter.

PO2

PDBS· δL+ signal — fed back to the laser and the MC.

FM1

FI
PO1

• Alignment control system.

Mirror alignment
control loop

· Wave-front sensing scheme.

PD· Sample small power with pick-off mirrors.

Interference fringe
control loop (δl-)

Mixer

Mixer

QPD

Mixer

PDPD

MixerδL x

Gravitational wave signal (δL-)

Common motion
control loop (δL+)

13EM1

Main interferometer with the 300-m arm cavities (2)— Operation of the main interferometer —• Main interferometer — operated over 4 hours.

Light power [a.u.] Light power [a.u.]· Laser source — 700 mW NPRO.
· With alignment control.
10.5

Transmitted power
Arm cavity 1
Arm cavity 20Dark fringe power

0.1

001

2
Time [hour]
1434

TAMA300 interferometer (1)— Operation of the whole interferometer —• TAMA300 interferometer isoperated under the Phase I configuration.
· 10 W laser source.
· Frequency of the master laser— controlled with the error signals of the MC and the interferometer.
· Slave laser — injection-locked to the master laser.

· 10 m ring mode cleaner.

· Pre-stabilize the laser frequency.
· Transmission of the modulation sidebands.
· Length is controlled with the δL+ signal of the interferometer.

· Main interferometer with the 300 m arm cavities.
· Controlled with the frontal modulation scheme.
· δL− signal — differentially fed back to the front mirrors.
· δl− signal — fed back to the beam splitter.
· δL+ signal — fed back to the laser and the MC.
· Alignment control for the arm cavities.
· Without power recycling.
15

TAMA300 interferometer (2)— TAMA300 interferometer for Phase I —Fabry-Perot-Michelson interferometerwith an arm length of 300 m
EM2

300 m arm cavity(NS arm)

Injection-locked
10 W laser
20 MHzMirroralignmentcontrolloopδL yDifferential motion
control loop (δL-)

FM2
Mixer

Injection locking
control loop

10 m Mode cleaner

Mixer

QPD
Mixer

300 m arm cavity (WE arm)

PD

Fiber LDPO2YAGIMOMPDBSFM1FIEOM

EOM
VCM

PO1

LD pumped
10 W laser
15.235 MHz

PD

20 MHz

NPRO
700 mWMixer

10 mringcavity

Mirror alignment
control loop

Interference fringe
control loop (δl-)

Mixer
EOM

EOM

PD

12 MHz

Mixer

Mixer

QPD

Mixer

PDPD

Mixer

δL x

EM
SUM

Laser frequency
stabilization loop

30 kHzGravitational wave signal (δL-)
MC mass loop
SUM

Feed around loop

Common motion
control loop (δL+)

16EM1

TAMA300 interferometer (3)— Lock acquisition —• Difficult to acquire the lock of the interferometer
only with the main control signals.
⇓Use auxiliary control signals.
extracted from the sampled beams from the pick-off mirrors.
Main control signals

Auxiliary control signals

δLx

δLyLaser & MC
One arm
lockedFront mirror

Anotherarm
lockedδl-δL-δL+

Beamsplitter
FringelockedFront mirrors(differentially)
Laser & MC

Turn off
Turn off

Controlled only with the main signals
17

TAMA300 interferometer (4)— Displacement noise level of the TAMA300 interferometer —• Preliminary sensitivity.
√−16m/ Hz.
Displacement noise level — 1 × 10

Displacement noise [m/Hz–1/2]–7

10–810–910–10
10–11
10–1210–1310–1410–15
10–16
10–1710–1810Seismic noise
Displacement noise
Shot noise anddetection system noise
Frequency noise

010110231010
Frequency [Hz]• Stability — operated over one hour.
18410510

TAMA300 interferometer (5)— Noise sources and problems —• Noise sources.
· ∼30 Hz — seismic noise.
· ∼500 Hz — alignment control system noise.
· 500 Hz ∼ — noises due to electronic circuits.
• Poor contrast and CMRR.
Contrast — 95.4%, CMRR — 44.
Probably, because of insufficient mode matching and alignment.
⇓Changed the mode-matching telescope
between the MC and the main interferometer.
⇓Mode matching — 97.8% → 99.8%.

19

Summary and future works• The TAMA300 interferometer isoperated with the final control configuration for the Phase I observation.
√−16m/ Hz.
· Sensitivity ∼ 1 × 10⇓
−19

• Improve the sensitivity → 5 × 10√
m/ Hz.

· Incident full laser power onto the PDs → improve the shot noise and detection system noise level.
· Optimize the alignment filter → reduce the alignment control system noise.
· Change the mode-matching telescope → improve the contrast and the CMRR.

• Realize stable operation.
· Low frequency drift control (beam pointing, beam centering, modulation frequency, ...).
· Improvement of the environment (vibration due to vacuum pumps, ...).

• Data-acquisition and analysis.
· Data-acquisition system.
· Calibration.
· Data analysis.
20

Locked-Fabry-Perot configuration (1)— Optical and control configuration —• Operate the both arm cavities with the 10 W laser source.
• Locked Fabry-Perot configuration.

20 MHzδLyMixer

Injection locking
control loopQPD

Mixer

Mixer

300 m arm cavity (WE arm)

PD

Fiber LD

PO2PD

YAG

IMOM

FI

EOM

EOM
VCM

PO1LD pumped
10 W laser
15.235 MHzPD

20 MHz

NPRO
700 mW

Mirror alignment
control loop

Mixer
EOM

QPD

EOM

PD

12 MHz

PD

PD

Mixer

EM

Laser frequency
stabilization loop

SUM

MC mass loop
δLx

Feed around loop

21Mixer

Locked-Fabry-Perot configuration (2)— Noise level —0101102

31010Frequency [Hz]22410510–1/2

NS arm cavity]

610510410310210110010–1
10–210–310–4
10–5
10–6
Deterctor noise
10Frequency noise [Hz/Hz

Displacement noise [m/Hz–1/2]

–6

10–7
10–8
10–9
10–10
10–11
10–12
10–13
10–14 WE arm cavity
10–15
10–16
10–17
10–1810