Double-resonance Optical Pumping Spectra Research Articles

Measuring the Hyperfine Splitting and Deriving the Hyperfine Interaction Constants of the Cesium 5p67d 2D5/2 Excited State

The measurement of the cesium (Cs) 5p67d2D5/2 excited state’s hyperfine splitting intervals and hyperfine interaction constants was experimentally investigated using a ladder-type (852 nm + 698 nm) three-level Cs system (5p66s2S1/2–5p66p2P3/2–5p67d2D5/2) with a room-temperature Cs atomic vapor cell. By scanning the 698 nm coupling laser’s frequency, the Doppler-free high-resolution electromagnetically-induced transparency (EIT)-assisted double-resonance optical pumping (DROP) spectra were demonstrated via transmission enhancement of the locked 852 nm probe laser. The EIT-assisted DROP spectra were employed to study the hyperfine splitting intervals for the Cs 5p67d2D5/2 excited state with a room-temperature Cs atomic vapor cell, and the radio-frequency modulation sideband of a waveguide-type electro-optic phase modulator (EOPM) was introduced for frequency calibration to improve the accuracy of frequency interval measurement. The existence of EIT makes the DROP spectral linewidth much narrower, and it is very helpful to significantly improve the spectroscopic resolution. Benefiting from the higher signal-to-noise ratio (SNR) and much better resolution of the EIT-assisted DROP spectra, the hyperfine splitting intervals between the hyperfine folds of (F” = 6), (F” = 5), and (F” = 4) of the Cs 5p67d2D5/2 state (HFS6″–5″ = −10.60(17) MHz and HFS5″–4″ = −8.54(15) MHz) were measured and, therefore, the magnetic dipole hyperfine interaction constant (A = −1.70(03) MHz) and the electrical quadrupole hyperfine interaction constant (B = −0.77(58) MHz) were derived for the Cs 5p67d2D5/2 state. These constants constitute an important reference value for an improvement of the precise measurement and determination of basic physical constants.

Fluorescence double resonance optical pumping spectrum and its application for frequency stabilization in millimeter scale vapor cells

In recent years, we are observing substantial efforts towards the miniaturization of atomic cells to a millimeter scale and below, with the ultimate goal of enabling efficient and compact light vapor interactions. However, such miniaturization results in a reduction in optical path, effectively reducing the contrast of the optical signal. In order to overcome this obstacle, we have introduced and demonstrated a new approach of fluorescence double resonance optical pumping (FDROP) in the ladder-type atomic system. We have developed a theoretical model to predict the FDROP spectrum and validated this model using experimental results in a millimeter-size cell. We show that the contrast of fluorescence signal of the FDROP approach is higher than the transmission signal in the double resonance optical pumping approach. Taking advantage of this desired property, we have used the FDROP for the purpose of stabilizing the frequency of a laser operating at the telecom waveband with the hyperfine structure of the 5P3/2–4D5/2 transition in a millimeter-size cell. By beating the stabilized laser to another stabilized laser, we obtained frequency instability floor of 9 × 10−10 at around 1000 s in terms of Allan deviation. Such sources which are stabilized to miniaturized cells may play an important building block in diverse fields ranging e.g. from communication to metrology.

Determination of the hyperfine structure constants of theRb87andRb854D5/2state and the isotope hyperfine anomaly

The hyperfine structure (hfs) splittings of the $4{D}_{5/2}$ state for two isotopes of $^{87}\mathrm{Rb}$ and $^{85}\mathrm{Rb}$ atoms are measured based on double-resonance optical pumping spectra in a $5{S}_{1/2}\text{\ensuremath{-}}5{P}_{3/2}\text{\ensuremath{-}}4{D}_{5/2}$ ladder-type atomic system. The frequency calibration is performed by employing a wideband fiber-pigtailed phase-type electro-optic modulator together with a Fabry-P\'erot cavity to cancel the error arising from nonlinear frequency scanning. The hfs magnetic dipole constant $A$ of the $4{D}_{5/2}$ state is determined to be \ensuremath{-}16.801 \ifmmode\pm\else\textpm\fi{} 0.005 MHz for $^{87}\mathrm{Rb}$ and \ensuremath{-}4.978 \ifmmode\pm\else\textpm\fi{} 0.004 MHz for $^{85}\mathrm{Rb}$. The hfs electric quadrupole constant $B$ of the $4{D}_{5/2}$ state is determined to be 3.645 \ifmmode\pm\else\textpm\fi{} 0.030 MHz for $^{87}\mathrm{Rb}$ and 6.560 \ifmmode\pm\else\textpm\fi{} 0.052 MHz for $^{85}\mathrm{Rb}$. The values of $A$ and $B$ for the $^{87}\mathrm{Rb}4{D}_{5/2}$ state are twice as accurate as previous work with thermal atoms using a femtosecond laser comb and the values of $A$ and $B$ for the $^{85}\mathrm{Rb}4{D}_{5/2}$ state are 3 times and 25 times more accurate than previous work in laser-cooled atoms using Fabry--P\'erot interferometer, respectively. According to this high precision of the hfs constants and the previously measured nuclear $g$ factors of the two isotopes, the value of the $d$-electron hyperfine anomaly $^{87}\mathrm{\ensuremath{\Delta}}{}^{85}(4{D}_{5/2})$ is derived to be \ensuremath{-}0.0041 \ifmmode\pm\else\textpm\fi{} 0.0009.

Off-resonant double-resonance optical-pumping spectra and their application in a multiphoton cesium magneto-optical trap

We present an investigation of double-resonance optical pumping (DROP) spectra under the condition of single-photon frequency detuning based on a cesium 6S1/2–6P3/2–8S1/2 ladder-type system with a room-temperature vapor cell. Two DROP peaks are found, and their origins are explored. One peak has a narrow linewidth due to the atomic coherence for a counterpropagating configuration; the other peak has a broad linewidth, owing to the spontaneous decay for a copropagating configuration. This kind of off-resonant DROP spectrum can be used to control and offset-lock a laser frequency to a transition between excited states. We apply this technique to a multiphoton cesium magneto-optical trap, which can efficiently trap atoms on both red and blue sides of the two-photon resonance.

Frequency stabilization of a laser diode to hyperfine structure of the 4D5/2 state of 85Rb atoms

We observed hyperfine structures of the 4D5/2 state of 85Rb atoms and applied them to the frequency stabilization of a laser diode by using the double resonance optical pumping (DROP). The hyperfine structures of the 4D5/2 states of 85Rb atoms were highly resolved in the Rb vapor cell. We compared the DROP with the optical–optical double resonance (OODR) in the 5S1/2–5P3/2–4D5/2 ladder-type system of 85Rb atoms. When we stabilized the frequency of a laser diode to the hyperfine structure of the 5P3/2(F″=4)–4D5/2(F″=3) transition by using the DROP spectrum, the frequency stability was approximately 2.3×10−12 after 100s.

Narrow-linewidth double-resonance optical pumping spectrum due to electromagnetically induced transparency in ladder-type inhomogeneously broadened media

Based on the cesium $6{S}_{1/2}$-$6{P}_{3/2}$-$8{S}_{1/2}$ ladder-type atomic system, double-resonance optical pumping (DROP) spectra including electromagnetically induced transparency (EIT) effects have been investigated with a room-temperature cesium vapor cell. For both cases of the probe and the coupling laser beams passing through the cesium vapor cell with the counter-propagation (CTP) and co-propagation (CP) configurations, the DROP spectra measured in the experiment display explicitly different linewidths. Thanks to the EIT effect, the linewidth of the DROP spectrum is explicitly narrower for the CTP configuration than for the CP configuration. Experimental results agree with the theoretical analysis considering Doppler averaging. Furthermore, when the coupling laser has moderate power, the DROP spectrum for the CTP configuration clearly shows two components: the narrow part due to the EIT effect and the broad part caused by optical pumping (but these two different components are never seen in the CP configuration). Also, the effect of the intensity of the coupling and probe lasers on the DROP spectra is investigated.

Improvement of the spectra signal-to-noise ratio of caesium 6P3/2–8S1/2 transition and its application in laser frequency stabilization

The spectra of the 133Cs 6P3/2–8S1/2 transition have been demonstrated by using both the double resonance optical pumping (DROP) and the optical–optical double resonance (OODR) techniques. Compared with the OODR technique, the DROP spectra show a much better signal-to-noise ratio and narrow spectral linewidth. When the frequency of a 795 nm external-cavity diode laser is stabilized to the DROP spectrum of 133Cs 6P3/2 F′ = 5–8S1/2 F″ = 4 transition, the lowest square root of the Allan variance of 4.1 × 10−12 at an averaging time of 100 s was obtained.

Frequency stabilization of a 13 μm laser diode using double resonance optical pumping in the 5P_3/2-6S_1/2 transition of Rb atoms

The frequency stabilization of a laser diode in the 1.3 microm region using double resonance optical pumping (DROP) spectrum in the 5P(3/2)-6S(1/2) transition of (87)Rb atoms is demonstrated. The signal-to-noise ratio of the DROP spectrum is approximately ten times higher than that of the previous optical-optical double resonance spectrum. The spectral linewidth of the DROP measures 8.4 MHz. When the frequency of a 1.367 microm laser diode is stabilized to the DROP spectrum, the frequency stability is 9 x 10(-12) after 100 s. Also, the wavelength of the frequency-stabilized laser locked to the 5P(3/2)-6S(1/2) transition using a wavelength meter is measured.

루비듐 5S1/2-5P3/2-4D3/2, 5/2전이선에서의 이중공명 광펌핑 분광

우리는 <TEX>$^{87}Rb$</TEX> 원자의 <TEX>$5S_{1/2}-5P_{3/2}-4D_{3/2,\;5/2}$</TEX> 전이선을 이용하여 레이저의 세기, 편광조합, 그리고 정렬상태에 따른 이중공명광펌핑(double resonance optical pumping; DROP) 스펙트럼을 조사하였다. <TEX>$5P_{3/2}-4D_{5/2}$</TEX> 전이선에서 레이저의 세기에 따른 초미세 구조간의 DROP 신호의 변화가 크게 나타났고, 그 원인은 순환전이선의 낮은 광펌핑 효율 때문이었다. 두 레이저의 편광조합을 달리 했을 때 이중공명의 전이율이 변하고, 이러한 효과가DROP스펙트럼의 변화로 나타났다. 또한 두 레이저가 같은 방향으로 진행하는 경우와 반대 방향으로 진행하는 경우를 비교했을 때, 스펙트럼의 선폭은 각각 12.2 MHz 와 6.9 MHz로 측정되었다. We present the double resonance optical pumping(DROP) spectra according to the laser power, the polarization combination of lasers, and the alignment of lasers in the transition <TEX>$5P_{3/2}-4D_{5/2}\;and\;5P_{3/2}-4D_{5/2}$</TEX> of <TEX>$^{87}Rb.$</TEX> We observed obviously changing DROP spectrum according to the laser power in the transition <TEX>$5P_{3/2}-4D_{5/2}$</TEX> involved the cycling transition. The laser power effects are attributed to the low optical-pumping-effect in the cycling transition. We observed changing DROP spectrum depending on the polarizations of the lasers. The laser polarization effects are attributed to the changing transition probability according to the polarizations of lasers. We compared the co-propagation with the counter-propagation and the spectral linewidths were 12.2 MHz and 6.9 MHz, respectively.

Double resonance optical pumping spectrum and its application for frequency stabilization of a laser diode

We present double resonance optical pumping (DROP) spectra for the 5P3∕2–4D3∕2 transition and the 5P3∕2–4D5∕2 transition of R87b and we use these spectra for frequency stabilization in the 1.5μm region. The spectra, compared to the conventional double resonance spectrum, show a good signal-to-noise ratio and a narrow spectral linewidth for laser frequency stabilization. The different intensities of the hyperfine states were attributed to the different rates of double resonance optical pumping into the other ground state. When we stabilized the frequency of a 1.5μm laser diode to the DROP spectrum, the best frequency stability was 1×10−11 after 100s.

이중공명 광펌핑을 이용한 1.5μm 반도체 레이저 주파수 안정화

우리는 이중공명 광펌핑(double resonance optical pumping; DROP)효과를 이용하여 루비듐(<TEX>$^{87}$</TEX> Rb) 원자의 5P<TEX>$_{3}$</TEX>2/-4D<TEX>$_{3}$</TEX>2/와 5P<TEX>$_{3}$</TEX>2/-4D<TEX>$_{5}$</TEX> 2/ 전이선에서 DROP 스펙트럼을 관측하고, 1.5 <TEX>$\mu\textrm{m}$</TEX> 레이저의 주파수를 무변조 안정화하였다. 관측한 DROP 스펙트럼은 기존의 광-광이중공명(optical-optical double resonance; OODR) 스펙트럼보다 높은 신호대잡음비를 가지며, 약 10 MHz의 좁은 선폭을 갖고 있다. DROP 스펙트럼의 상대적인 세기는 자발방출에 의한 광펌핑 정도로 설명할 수 있었다. DROP스펙트럼에 안정화된 1.5 <TEX>$\mu\textrm{m}$</TEX> 레이저의 주파수 흔들림은 샘플링 시간 0.1초에서 0.2 MHz로 측정되었고, 상대주파수 흔들림은 평균시간 100초에서 약 1<TEX>${\times}$</TEX><TEX>$10^{-11}$</TEX>이었다. We present the double resonance optical pumping(DROP) spectra in the transition 5P<TEX>$_{3}$</TEX>2/-4D<TEX>$_{3}$</TEX>2/ and 5P<TEX>$_{3}$</TEX>2/-4D<TEX>$_{5}$</TEX> 2/ of (<TEX>$^{87}$</TEX> Rb) and the frequency stabilization in the <TEX>$1.5mutextrm{m}$</TEX> region using those spectra. Those spectra have high signal-to-noise ratio and narrow spectral linewidth, which is about 10 MHz. We could account fur the relative intensities of the hyperfine states of those spectra by the spontaneous emission into the other state. When the frequency of the <TEX>$1.5mutextrm{m}$</TEX> laser diode was stabilized to the DROP spectrum, the frequency fluctuation was about 0.2 MHz fDr sampling time of 0.1 s and the Allan deviation(or the square root of the Allan variance) was about 1<TEX>${\times}$</TEX>10<TEX>$^{-11}$</TEX> for averaging time of l00s.