{"id":2661,"date":"2023-01-15T12:21:56","date_gmt":"2023-01-15T04:21:56","guid":{"rendered":"https:\/\/comblaser.phy.ncu.edu.tw\/?page_id=2661"},"modified":"2025-11-10T14:46:24","modified_gmt":"2025-11-10T06:46:24","slug":"absolute-frequency-of-rubidium-optical-clock-without-frequency-modulation","status":"publish","type":"page","link":"https:\/\/comblaser.phy.ncu.edu.tw\/index.php\/absolute-frequency-of-rubidium-optical-clock-without-frequency-modulation\/","title":{"rendered":"Absolute Frequency of Rubidium Optical Clock without Frequency Modulation<\/strong>"},"content":{"rendered":"\n

Absolute Frequency of Rubidium Optical Clock without Frequency Modulation<\/h2>\n\n\n\n

Chi-Hsiang Chu, Yu-Jhe Shin, Yi-Ting Lin*, Wang-Yau Cheng<\/p>\n\n\n\n

Abstract<\/p>\n\n\n\n

We have measured the clock transition of rubidium. Using the cross-over frequency locking method developed by our team, we have achieved frequency-stabilized and frequency-scanning system only using one 778 nm laser. Moreover, we used a Helmholtz coil to reduce the influence of the Zeeman shift and learned about the coefficient of 87<\/sup>Rb\u00a0 5S 1\/2<\/sub>(F = 2) \u2192 5D 5\/2<\/sub>(F = 4) is \u221248.9 \u00b1 2.6 kHz\/G. We also build a vacuum system (~ \u301610\u3017^(-7) Torr) to measure Rb self-collision shift and found that the linear coefficient is \u2212120\u00b170 Hz\/\u00b5Torr. Furthermore, the Allan deviation of our system can reach 3\u00d7\u301610\u3017^(-13) within 1000 seconds of integration time. Finally, we have measured the rubidium 5S 1\/2<\/sub> (F = 3) \u2192 5D 5\/2<\/sub>(F = 1 \u223c 5) transition and only \u00b15 kHz difference between our results and the suggested value of Certificate in Investment Performance Measurement(CIPM).\u00a0<\/p>\n\n\n\n

Set up<\/h2>\n\n\n\n

<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n
\n
\"\"
Fig.(1) Invar Fabry-Perot Cavity<\/strong>
We choose Invar, a metal with a low coefficient of thermal expansion as the material for our cavity. The specific heat capacity and the thermal conductivity of Invar is lower than cropper and difficult to control temperature. We use temperature controller to control the temperature and stabilize the length of the cavity.<\/figcaption><\/figure>\n<\/div>\n\n
\n
\"\"
Fig.(2) Penetrating Light at Output of F.P Cavity<\/strong>
Finesse=6281\uff0cFSR=986.15 MHz<\/figcaption><\/figure>\n<\/div>\n\n
\n
\"\"
Figure 3: PDH and Penetrating Light<\/strong>
PDH frequency lock is to feed back the high-frequency signal within 30kHz to
AOM, and the low-frequency signal below 100Hz frequency drift feed back to the laser PZT.
<\/figcaption><\/figure>\n<\/div>\n\n\n

Frequency locking and scanning\u00a0 system<\/h2>\n\n\n
\n
\"\"
Fig.(4) Rb Glass Cell 2<\/strong>
Use Helmholtz coil to produce zero magnetic field to remove Zeeman shift influence.<\/figcaption><\/figure>\n<\/div>\n\n\n

<\/p>\n\n\n\n

\n
\"\"
Fig.(5) Rb\u00a0 Vacuum Cell 2<\/strong>

Since the absolute frequency value obtained in Fig.(4) has a gap with CIPM, we suspect that the frequency shift is caused by collision shift, so we made a vacuum chamber to measure.<\/figcaption><\/figure>\n<\/figure>\n\n\n\n

<\/p>\n\n\n\n

Crossover<\/h2>\n\n\n
\n
\"\"
Fig.(6) Lock Frequency with Crossover Line Locking Method<\/strong> on 85<\/sup>Rb Spectroscopy<\/strong>
Our group found that if you have a laser frequency f and another optical path uses Fiber EOM to modulate
its frequency to F+f, we found that their cross over has a certain probability at the frequency of\u00a0 (F+f)\/2\u00a0
make atom transit, we call it cross-over spectroscopy.<\/figcaption><\/figure>\n<\/div>\n\n
\n
\"\"
Fig.(7) Lock Frequency with Crossover Line Locking Method<\/strong> on 87<\/sup>Rb Spectroscopy<\/strong><\/figcaption><\/figure>\n<\/div>\n\n
\n
\"\"
Fig 8.The Allan Variance of 778 nm Frequency Stabilized<\/strong> Laser and Comb laser (refer to Cs clock )<\/strong><\/figcaption><\/figure>\n<\/div>\n\n
\n
\"\"
Fig.(9)Absolute Frequency for Glass Cell 85Rb and CIPM Recommendations<\/strong><\/figcaption><\/figure>\n<\/div>\n\n
\n
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Fig.(10)85Rb Absolute Frequency in Vacuum Chamber and CIPM Recommendations<\/strong><\/figcaption><\/figure>\n<\/div>\n\n\n

conclusion<\/h2>\n\n\n\n

(1.)We successfully confirmed by measurements in vacuum Rb chamber that our previous difference in absolute frequency\u00a0measurements came from frequency shifts caused by gases of different elements<\/p>\n\n\n\n

(2.)We use only one 778nm Fiber laser to perform frequency sweep and frequency lock at the same time through the cross-over spectroscopy.<\/p>\n\n\n\n

(3) The rubidium atomic optical clock we made has a stability of 5 \u00d7 \u301610\u3017^(-12) within 1 second integral time, reaching 3 \u00d7 \u301610\u3017^(-13) \u00a0within 1000 second of integration time.<\/p>\n","protected":false},"excerpt":{"rendered":"

Absolute Frequency of Rubidium …<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-2661","page","type-page","status-publish","hentry"],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/comblaser.phy.ncu.edu.tw\/index.php\/wp-json\/wp\/v2\/pages\/2661","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/comblaser.phy.ncu.edu.tw\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/comblaser.phy.ncu.edu.tw\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/comblaser.phy.ncu.edu.tw\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/comblaser.phy.ncu.edu.tw\/index.php\/wp-json\/wp\/v2\/comments?post=2661"}],"version-history":[{"count":14,"href":"https:\/\/comblaser.phy.ncu.edu.tw\/index.php\/wp-json\/wp\/v2\/pages\/2661\/revisions"}],"predecessor-version":[{"id":2697,"href":"https:\/\/comblaser.phy.ncu.edu.tw\/index.php\/wp-json\/wp\/v2\/pages\/2661\/revisions\/2697"}],"wp:attachment":[{"href":"https:\/\/comblaser.phy.ncu.edu.tw\/index.php\/wp-json\/wp\/v2\/media?parent=2661"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}