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ASTROD Symposium 2006, July 14-16, Beijing. The Development of Optical Frequency Standards and its Application to Space Missions. Naicheng Shen. Joint Laboratory of Advanced Technology in Measurements

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The development of optical frequency standards and its application to space missions

ASTROD Symposium 2006, July 14-16, Beijing

The Development of Optical Frequency Standards and its Application to Space Missions

Naicheng Shen

Joint Laboratory of Advanced Technology in Measurements

(中科院计量测试高技术联合实验室), Institute of Physics Chinese Academy of Sciences, Beijing 100080


The development of optical frequency standards and its application to space missions

ASTROD Symposium 2006, July 14-16, Beijing

Outline

  • Motivation and Background

  • Optical Frequency Standards

  • 532 nm Iodine Stabilized Nd:YAG Laser

  • Optical Frequency Comb

  • A Method of Synchronization of Clocks Using

  • Signals From Orbiting Satellite such as GPS


The development of optical frequency standards and its application to space missions

ASTROD Symposium 2006, July 14-16, Beijing

Motivation

  • To develop optical frequency standads

  • To improve on reproducibility of 532 nm iodine

    stabilized Nd:YAG laser

  • To pursue phase control femtosecond laser

  • To develop optical frequency comb

  • To develop a new technology for synchronization of clocks


The development of optical frequency standards and its application to space missions

Authors

Lab

Atoms and transitionsR /m1

Andreae et al.(1992)

MPQ

H:1S-2S 10 973 731.568 41(42)

Nez et al. (1992)

LKB

H:2S-8S/8D 10 973 731.568 30(31)

Weitz et al. (1995)

MPQ

H:1S-2S 10 973 731.568 44(31)

Bourzeix et al. (1996)

LKB

H:2S-8S/8D 10 973 731.568 36(18)

de Beauvoir et al. (1997)

LKB

LPTF

H,D:2S-8S/8D 10 973 731.568 59(10)

Udem et al. (1997)

MPQ

H:1S-2S 10 973 731.568 639(91)

ASTROD Symposium 2006, July 14-16, Beijing


The development of optical frequency standards and its application to space missions

ASTROD Symposium 2006, July 14-16, Beijing

Df1

F

Optical frequency comb

Control the carrier envelope phase offset (CEO) is a very important topics in ultrafast science and frequency metrology.

E(w,t) =E0(t)exp(iw t+f)

CEO lead to the comb shift

Df =2pd /F

Repetition rate

f= c /2nl

Longtitudinal mode frequency

fn=d+nF

D.J.Jones et al., Science 288, 635(2000)


The development of optical frequency standards and its application to space missions

ASTROD Symposium 2006, July 14-16, Beijing

fs laser spetrum

Broaden the femtosecond laser spectrum to cover an octave by photonic crystal fiber (PCF).

f1=d+nF

f2=d+2nF

Heterodyne measure the beat of 2f1and f2 will reveal the signal d

2 f1 - f2 = 2(nF+d) -(2nF+d ) = d



The development of optical frequency standards and its application to space missions

Frequency Measurement Experimental Layout

antenna

Reference

10MHz

Phase loop for repetition rate

Phase loop for CEO

Pump

Laser

PCF

Grating


The development of optical frequency standards and its application to space missions

532 nm iodine stabilized Nd:YAG

frequency standard

  • Dr R. L. Byer Groups, Stanford University, 1992

  • Unprecedented frequency stability: 510-14(1 s), 510-15(after 400 s) , Dr J. L. Hall Groups , JILA,1999

  • Frequency stability: 510-14 (relative short term), 610-15 (longer durations), BIPM, 2001

  • New hyperfine structure transitions and frequency stability and reproducibility had obtained exciting results at AIST

  • Absolute frequency measurements have been developed in several countries

  • The accuracy and long term stability are similar to the small Cs clock of

  • CCTV

  • The short term stability depend on itself

  • Specifications

  • Refer to the small Cs clock (HP-5071


The development of optical frequency standards and its application to space missions

ASTROD Symposium 2006, July 14-16, Beijing

Aperture

Aperture

Side view

Reflection

Prism

Temperature control of I2 cell

Reflection

Prism

PBS3

EOM

PD & pre-amplifier

532nm

Aperture

AOM

Nd:YAG Laser

1064nm

/4

PBS2

PBS1

/2

/2

35 cm × 70 cm

Optical Parts of 532nm I2-stabilizedNd:YAG Laser


The development of optical frequency standards and its application to space missions

4.Applied 3-stage cooling 5. Using a sealed box for 6. The temperature is set ensured lower temperature isolating the cooling at - 18C, a vapor

components pressure of 0.54 Pa

ASTROD Symposium 2006, July 14-16, Beijing

Molecular Iodine Absorption Cell

quartz glass

3-stage cooling

Sealed box

3.Filled with highly pure iodine

at AIST of Japan or

JLAST,CAS, China

Cold finger

2.Baked and vacuumized

3 days continuously

Temperature control

components pressure of 0.54 Pa

1.Windows are optically

contacted to the tube

4.Applied 3-stage cooling 5. Using a sealed box for 6. The temperature is set ensured lower temperature isolating the cooling at - 18C, a vapor


The development of optical frequency standards and its application to space missions

ASTROD Symposium 6. The temperature is set ensured lower temperature isolating the cooling at - 182006, July 14-16, Beijing

Optical Extending in Lengthways

and Transverse Orientation

Bigger beam diameter benefit

for increasing transverse transit time

Low vapor pressure

Narrow linewidth

Good SNR


The development of optical frequency standards and its application to space missions

ASTROD Symposium 6. The temperature is set ensured lower temperature isolating the cooling at - 182006, July 14-16, Beijing

Modulated probe beam

Frequency stabilized electrics

PD & pre-amplifier

Filter and amplifier

AOM

10MHz

80MHz

Frequency synthesizer

Rubidium clock

Monolithic ring laser and SHG

AOM Drive

EOM

Slow

Fast

IF

EOM Driver

Servo control

PI control

RF

LO

Phase shift

Oscillator

DBM

Electrics Parts of I2-stabilized Nd:YAG Laser


The development of optical frequency standards and its application to space missions

ASTROD Symposium 6. The temperature is set ensured lower temperature isolating the cooling at - 182006, July 14-16, Beijing

Beat Frequency measurements


The development of optical frequency standards and its application to space missions

ASTROD Symposium 6. The temperature is set ensured lower temperature isolating the cooling at - 182006, July 14-16, Beijing

Allan Standard Deviation of Each Laser (10-15 )


The development of optical frequency standards and its application to space missions

ASTROD Symposium 6. The temperature is set ensured lower temperature isolating the cooling at - 182006, July 14-16, Beijing


The development of optical frequency standards and its application to space missions

Frequency Shift Measurements 6. The temperature is set ensured lower temperature isolating the cooling at - 18

ASTROD Symposium 2006, July 14-16, Beijing

Pressure frequency shift

Power frequency shift


The development of optical frequency standards and its application to space missions

Theoretical and Current Observed Linewidths of 6. The temperature is set ensured lower temperature isolating the cooling at - 18

Trapped Ion Clock Transitions

Ion Clock (nm) Theoretical Current Lowestune.(1)

(Hz) transitiuon linewidth(Hz) linewidth(Hz) of fre. meas.(Hz)

199Hg + 2S 1/2-2D 5/2 282 1.7 6.7 10

171Yb + 2S 1/2-2D 3/2 435 3.1 30 6

88Sr + 2S 1/2-2D 3/2 674 0.4 70 100

115In + 1S 0-3P0 236 0.8 170 230

171Yb + 2S 1/2-2F 7/2 467 ~10-9 180 230

40Ca + 2S 1/2- 2D5/2 729 0.2 1000

  • Frequency value of 40Ca + was not recommended by CIPM as reference for the

  • Realization of the meter


The development of optical frequency standards and its application to space missions

Contributions to the standard uncertainty of the 6. The temperature is set ensured lower temperature isolating the cooling at - 1840Ca optical frequency

standard determined at T=3 mK and envisaged for T=6 K

Effect T=3mK(Hz) T=6K (mHz)

Residdual fist-order Doppler effect 2.6 150

Second-order Doppler effect 0.005 0.025

Asymmetry of line shape 0.05 50

Other phase Contributions4 100

Magnetic field(60Hz mT-2) 0.1 80

Quadratic Stark effect 0.06 20

(|E|<2V cm -1)

Blackbody radiation 4.3 50

Servo electronics 3.2 100

Influence of cold atom coll 1.8 260

Statistical uncertainty of 3 <5

frequency comparison

Total uncertainty  8350

Total relative uncertainty  /  2 10 –14 8 10 -16


The development of optical frequency standards and its application to space missions

ASTROD Symposium 6. The temperature is set ensured lower temperature isolating the cooling at - 182006, July 14-16, Beijing

The optical part of Sr atom apparatus,six Brewster’s windows are

input sides of lasers , cool trapped Sr atoms are in the center part


Developing definition of second and frequency standards
Developing Definition of Second 6. The temperature is set ensured lower temperature isolating the cooling at - 18and Frequency Standards

Cold atom microwave frequency standards: Cs,Rb

Optical cold atom frequency standards : Ca, Mg, Sr

Ion frequency standards : : 199Hg +,115In + ,88Sr + ,

87Sr + , 171Yb + ,Ca +

CIPM – CCTF adopted a 2001resolution to seek secondary ‘representations’ of the second. Such representations can be based on

the different cold ion and atom standards ,both optical and microwave,

and would be able to take full advantage of improved stability and

reproducibility, but remain limited to the caesium accuracy. This

position represents a useful intermediate stage for evaluating the

systematics of different systems prior to making any rational choice

for a new time definition.


The development of optical frequency standards and its application to space missions

ASTROD Symposium 6. The temperature is set ensured lower temperature isolating the cooling at - 182006, July 14-16, Beijing

Method of synchronization between satellite clock B and earth

reference clock A:

1. Define the characteristic parameter of relative motion :

assume that A sends two signals to B which are spaced tA seconds apart according to clock A. Due to the relative motion

of A and B, the two signals will arrive at B with a different time spacing as measured by B. The parameter  is simply the

ratio of the latter time spacing to the former, i.e., the two

signals arrive with time spacing tA according to clock B. Because the relative motion is uniform,  does not depend on

tA . If there is no relative motion between A and B,  = 1.

2. If B sends two signals to Awhich are spaced tB seconds apart according to clock B. According relativity principle, the two signals will arrive at A with time spacing  tB as measured by A. From the definition of  given above, we see that

 = (t2B– t1B)/(t2A– t1A) = (t3A– t2A )/(t2B– t1B)

 =[(t3A– t2A )/(t2A– t1A )]1/2


The development of optical frequency standards and its application to space missions

Locking 6. The temperature is set ensured lower temperature isolating the cooling at - 18

Without Locking


The development of optical frequency standards and its application to space missions

ASTROD Symposium 6. The temperature is set ensured lower temperature isolating the cooling at - 182006, July 14-16, Beijing

Method of Synchronization

If B were synchronized to A, the time reading t1Band t2B would become

s1Band s2B . This is accomplished by determining s1B , which determines the

correction s1B - t1B that needs to be applied, defined as  B .

One determines s1B by assuming the clocks were synchronized , so that each would indicate the same time t0 at the fictional moment of spatial coincidence. Imaging that A sends a radio signal at that very moment.

The signal is simultaneously received at time t0 according to synchronized clock B. We have  = (s1B– t0)/(t1A– t0) = (t2A– t0)/(s1B– t0) , 2 = (t2A– t0)/(t1A– t0)

Then,

t0= (2t1A– t2A)/(2 –1) , s1B= (t2A +t1A)/(+1).

Define the starred distance d1ABfrom A to B at the instant s1B of

reception of the signal sent by A at time t1A , as follow: d1AB= c (s1B– t1A),

where c is the speed of light as it travels from A to B. Then

d1AB= c (t2A– t1A)/(+1).

Now define the starred radial velocity vrAB between A and B as follow:

vrAB=d1AB/s1B= [c (t2A–t1A)/(+1)]/[(t2A+t1A)/(+1)] =c (t2A–t1A)/(t2A+t1A)

= c (-1)/.


The development of optical frequency standards and its application to space missions

ASTROD Symposium 6. The temperature is set ensured lower temperature isolating the cooling at - 182006, July 14-16, Beijing

  • 1. Define the characteristic parameter of relative motion :

  • assume that A sends two signals to B which are spaced tA seconds apart according to clock A. Due to the relative motion of A and B, the two signals will arrive at B with a different time spacing as measured by B.The parameter  is simply the ratio of the latter time spacing to the former, i.e., the two signals arrive with time spacing tA according to clock B. Because the relative motion is uniform,  does not depend on tA.If there is no relative motion between A and B,  = 1.

  • If B sends two signals to A which are spaced tB seconds apart according to clock B. According relativity principle, the two signals will arrive at A with time spacing tB as measured by A. From the definition of  given above, we see that

  •  = (t2B – t1B )/(t2A – t1A )

  • = (t3A – t2A )/(t2A – t1A )

  •  =[(t3A – t2A )/(t2A – t1A )]1/2

Method of synchronization between satellite clock B and earth reference clock A:


The development of optical frequency standards and its application to space missions

ASTROD Symposium 6. The temperature is set ensured lower temperature isolating the cooling at - 182006, July 14-16, Beijing


The development of optical frequency standards and its application to space missions

One determines 6. The temperature is set ensured lower temperature isolating the cooling at - 18s1B by assuming the clocks were synchronized, so that each would indicate the same timet0 at the fictional moment of spatial coincidence. Imaging that A sends a radio signal at that very moment. The signal is simultaneously received at time t0 according to synchronized clock B. We have

 = (s1B– t0)/(t1A– t0) = (t2A– t0)/(s1B– t0 ) ,

2 = (t2A– t0)/(t1A– t0)

Then, t 0= (2t1A– t2A)/(2 –1) ,

s1B= (t2A+t1A)/(+1).

Define the starred distance d 1ABfrom A to B at the instant s1B of

reception of the signal sent by A at time t1A , as follow:

d 1AB= c (s1B– t1A),

where c is the speed of light as it travels from A to B. Then d1AB = c (t2A– t1A)/(+1).

Now define the starred radial velocity v rAB between A and B as follow:

v rAB=d 1AB/s 1B= [c (t2A–t1A)/(+1)]/[(t2A+ t1A)/(+1)]

= c (t2A–t1A)/(t2A+t1A)= c (-1)/.

ASTROD Symposium 2006, July 14-16, Beijing

Method of Synchronization

If B were synchronized to A, the time reading t1Band t1B would become s1Band s2B . This is accomplished by determining s1B , which determines the correction s1B - t1B that needs to be applied, defined as B .


The development of optical frequency standards and its application to space missions

ASTROD Symposium 6. The temperature is set ensured lower temperature isolating the cooling at - 182006, July 14-16, Beijing

The End

Thank you for your attention!