Transition Of Iodine Research Articles

Iodine spectrometer based on a 633 nm transmission-grating diode laser

We report a new iodine spectrometer for absolute frequency measurements of various transitions of molecular iodine in the 633 nm region. To obtain good frequency accuracy, the laser beams used in spectroscopy have been optimized for spatial and spectral quality. This is achieved by injection locking a microlensed diode laser with nearly Gaussian output beam to an external-cavity diode laser. The external-cavity laser has been designed for enhanced frequency stability and reproducibility by minimizing the effects of ambient pressure and temperature, and by utilizing transmission-grating geometry for compact and robust structure. The high stability combined with the invariant output beam pointing makes the laser design adaptable also for other purposes of length metrology and atom optics.

Molecular Iodine Spectra and Laser Stabilization by Frequency-Doubled 1534 nm Diode Laser

By using the second harmonic radiation of a 1543 nm diode laser, several predicted rovibronic transitions of molecular iodine were observed for the first time. We demonstrated that the absolute frequency of a 1534 nm external-cavity diode laser could be frequency-stabilized to a 1 MHz instability (for one second averaging time) by locking the frequency of the second harmonic generation to the dense rovibronic spectrum of 127I2. Our scheme shows one possible means of generating a frequency grid in the entire wavelength region of optical communications.

Continuous-wave laser oscillation on the 1315nm transition of atomic iodine pumped by O2(a1Δ) produced in an electric discharge

Laser action at 1315nm on the I(P1∕22)→I(P3∕22) transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O2(a1Δ) which is produced using wet-solution chemistry. The difficulties in chemically producing O2(a1Δ) has motivated investigations into purely gas phase methods to produce O2(a1Δ) using low-pressure electric discharges. In this letter, we report on the demonstration of a continuous-wave laser on the 1315nm transition of atomic iodine where the O2(a1Δ) used to pump the iodine was produced by a radio-frequency-excited electric discharge. The electric discharge was sustained in a He∕O2 gas mixture upstream of a supersonic cavity which is employed to lower the temperature of the continuous gas flow and shift the equilibrium of atomic iodine in favor of the I(P1∕22) state. The laser output power was 220mW in a stable cavity composed of two 99.99% reflective mirrors.

Path to the measurement of positive gain on the 1315-nm transition of atomic iodine pumped by O/sub 2/(a/sup 1//spl Delta/) produced in an electric discharge

Laser action at 1315 nm on the I(/sup 2/P/sub 1/2/)/spl rarr/I(/sup 2/P/sub 3/2/) transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O/sub 2/(a/sup 1//spl Delta/) which is produced using wet-solution chemistry. The system difficulties of chemically producing O/sub 2/(a/sup 1//spl Delta/) have motivated investigations into gas phase methods to produce O/sub 2/(a/sup 1//spl Delta/) using low-pressure electric discharges. We report on the path that led to the measurement of positive gain on the 1315-nm transition of atomic iodine where the O/sub 2/(a/sup 1//spl Delta/) was produced in a flowing electric discharge. Atomic oxygen was found to play both positive and deleterious roles in this system, and as such the excess atomic oxygen was scavenged by NO/sub 2/ to minimize the deleterious effects. The discharge production of O/sub 2/(a/sup 1//spl Delta/) was enhanced by the addition of a small proportion of NO to lower the ionization threshold of the gas mixture. The electric discharge was upstream of a continuously flowing supersonic cavity, which was employed to lower the temperature of the flow and shift the equilibrium of atomic iodine more in favor of the I(/sup 2/P/sub 1/2/) state. A tunable diode laser system capable of scanning the entire line shape of the (3,4) hyperfine transition of iodine provided the gain measurements.

Structural phase transitions in iodine under high pressure

Abstract High-pressure powder X-ray diffraction experiments have been carried out on solid iodine at room temperature. A new intermediate phase V has been identified in the pressure range 24–28 GPa, in the close vicinity of the pressure-induced molecular dissociation. The structure is incommensurately modulated, a rare case for elemental solids. The nearest interatomic distances are distributed over a range 2.8–3.2 Å, which characterizes phase V as a transient state between the molecular and monatomic states. We discuss the overall change of the crystal structure of iodine with pressure, which gives an insight into the process of molecular formation and dissociation.

Phase transition in iodine: a chemical picture

The phase transition under pressure in iodine is analyzed using the electron localization function (ELF), explaining that the increase of the c/ a ratio under compression is due to the presence of the lone pairs. A probabilistic interpretation is given for ELF.

Measurement of positive gain on the 1315nm transition of atomic iodine pumped by O2(a1Δ) produced in an electric discharge

Laser action at 1315nm on the I(P1∕22)→I(P3∕22) transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O2(a1Δ), which is produced using wet-solution chemistry. The system difficulties of chemically producing O2(a1Δ) has motivated investigations into gas phase methods to produce O2(a1Δ) using low-pressure electric discharges. In this letter we report on positive gain on the 1315nm transition of atomic iodine where the O2(a1Δ) was produced in a flowing electric discharge. The electric discharge was followed by a continuously flowing supersonic cavity that was necessary to lower the temperature of the flow and shift the equilibrium of atomic iodine more in favor of the I(P1∕22) state. A tunable diode laser system capable of scanning the entire line shape of the (3,4) hyperfine transition of iodine provided the measurements of gain.

Investigation of single-factor calibration of the wave-number scale in Fourier-transform spectroscopy

We have used the fundamental and frequency-doubled output of a single-frequency tunable laser locked to a precisely known transition in molecular iodine to provide calibration of a Fourier-transform spectrometer (FTS) in the visible and near-ultraviolet regions and to investigate the limiting uncertainty involved in calibrating spectra by using a single multiplicative correction to the entire optical frequency scale. An integrating sphere was used to introduce the laser light as a pseudoincoherent source and provide uniform illumination of the FTS field of view. The sphere also served to combine the laser beams with light from a series of mercury electrodeless discharge lamps containing argon carrier gas at selected pressures. Four strong lines in the spectrum of 198Hg were measured with these lamps to obtain precise wavelengths and argon-pressure-shift coefficients. These lines, emitted from lamps with argon pressures in the range 33 Pa (0.25 Torr) to 1330 Pa (10 Torr), are suitable for future calibration of FT spectra without need for the laser source. The limiting relative uncertainty component in the reported wavelengths is 6.19×10−9, as estimated from observed deviation of the frequency ratios of the calibration lasers from the exact value of 2. The adequacy of a single multiplicative correction factor for the absolute calibration of an individual FT spectrum is supported by our data, at the level of better than a part in 108.

Frequency stabilization of a 1319-nm Nd:YAG laser by saturation spectroscopy of molecular iodine.

Hyperfine transitions of molecular iodine were observed by use of the frequency-doubled output of a 1319-nm Nd:YAG laser with saturation spectroscopy. The laser frequency was stabilized to the observed hyperfine transition and reached a stability of 6 x 10(-12) for a 1.5-s averaging time, improving toward the 1 x 10(-12) level after 100 s. The iodine-stabilized 1319-nm Nd:YAG laser is an excellent candidate for an optical frequency standard for telecommunication applications.

Frequency measurements and hyperfine structure of the R(85)33–0 transition of molecular iodine with a femtosecond optical comb

Absolute frequency measurements of the R(85)33–0 transition of molecular iodine at the blue end of the tuning range of a frequency-doubled Nd:YAG laser are implemented with a femtosecond optical comb based on a mode-locked Ti:sapphire laser. The hyperfine structure of the R(85)33–0 transition is observed by use of high-resolution laser spectroscopy and is measured by the femtosecond optical comb. The observed hyperfine transitions are good frequency references for both frequency-doubled Nd:YAG and Nd:YVO4 lasers in the 532-nm region. High-accuracy hyperfine constants are obtained by our fitting the measured hyperfine splittings to a four-term Hamiltonian, which includes the electric quadrupole, spin–rotation, tensor spin–spin, and scalar spin–spin interactions.

Optical pumping of the <inline-formula><math display="inline" overflow="scroll"><mi>XeF</mi><mo>(</mo><mstyle mathvariant="normal"><mtext>C</mtext></mstyle><mo>→</mo><mstyle mathvariant="normal"><mtext>A</mtext></mstyle><mo>)</mo></math></inline-formula> and iodine 1.315-μm lasers by a compact surface discharge system

Details are provided regarding the design, construction, and performance of a compact ('0.6-m 2 footprint), single-channel surface discharge system and its application to optically pumping the XeF(C !A) and iodine atomic lasers in the blue-green ('480 nm) and near infrared (1.315 mm), respectively. The system has a gain (active) length of '50 cm, and triggering the discharge requires no high-voltage or high-current switches. Measurements of the velocity of the photodisso- ciation bleaching wave and the small-signal gain of the XeF(C!A) sys- tem are described. At 488 nm, the gain coefficientg was found to be '0.3% cm 21 , a value comparable to those reported previously for sys- tems dissipating considerably higher power per unit length. Single-pulse energies .50 mJ from the XeF(C!A) laser ('485 nm) and .0.7 J on the 5p 2 P1/2!5p 2 P3/2 transition of atomic iodine at 1.315 mm have been obtained with nonoptimized resonator output couplings (5% and 10%, respectively). The rate of erosion of the dielectric surface has been mea- sured to be '0.1 to 0.3 mm/shot for a glass ceramic dielectric, and the performance of two electrical configurations for the ballasting pins (feedthrough and V) is compared. © 2003 Society of Photo-Optical Instrumenta-

Laser light sources for space-based gravitational wave detectors

This contribution summarizes recent progress in the development of diode-pumped Nd:YAG lasers suited for applications in laser-based metrology. Applying an unstable resonator design to a monolithic ring laser, 2 W single-frequency output power in a diffraction-limited beam is generated. Injection locking was used to increase the available power even further. Finally, techniques to improve the free-running lasers intensity and frequency stability are demonstrated. Low intensity noise is accomplished by application of an electronic feedback loop. Low frequency noise is achieved by stabilization onto a hyperfine transition of molecular iodine.

Iodine stabilized dye laser system for frequency measurements in the visible and near ir region of the spectrum

An iodine stabilized dye laser system is described that provides traceable measurement of reference frequencies in the visible spectrum from 540 to 670 nm and in the near infrared at 1.15 /spl mu/m. The system allows calibration of the widely used 633 nm, 612 nm, and 543 nm HeNe laser systems. Also, frequency measurements of a polarization stabilized 1153 nm HeNe laser have been performed via frequency doubling and comparison with the dye system operating on the corresponding 576 nm lines. Studies of the shift sensitivities of the system at various wavelengths of interest are described for variation of iodine cell pressure, laser modulation amplitude, and optical saturation power. The dye system was also stabilized to hyperfine components associated with the 6-3 P(33) iodine transition and compared with a 633 nm iodine stabilized HeNe standard.

An iodine stabilized laser source at two wavelengths for accurate dimensional measurements

A tunable laser system is described that provides wavelength references at both 633 and 640 nm by locking to hyperfine components of molecular iodine using a simple external cell technique. The frequency uncertainty at each wavelength is less than 1 MHz and no calibration of the frequencies is required as they are both referenced to iodine transitions. Switching between references requires a simple adjustment of laser wavelength that produces no change in beam alignment. At either wavelength the laser provides more than 3 mW of unused light that is not modulated, making it useful for dimension measuring interferometry. The measurement of the diameter of silicon spheres to 2×10−8 is given as an example.

Hyperfine structure and absolute frequency determination of the R(1 2 1)35-0 and P(1 4 2)37-0 transitions of [formula omitted] near 532 nm

Hyperfine structures of the R(1 2 1)35-0 and P(1 4 2)37-0 transitions of molecular iodine at the blue end of the tuning range of a frequency-doubled Nd:YAG laser are measured by using two I 2-stabilized lasers. The absolute frequencies of the observed transitions are determined by a frequency link to an optical frequency reference (the R(5 6)32-0:a 10 hyperfine transition), using an optical frequency comb generator. The observed hyperfine transitions are good frequency references for both frequency-doubled Nd:YAG and Nd:YVO 4 lasers in the 532 nm region. High-accurate hyperfine constants are obtained for the P(1 4 2)37-0 transition by fitting the measured hyperfine splittings to a four-term Hamiltonian, which includes the electric quadrupole, spin–rotation, tensor spin–spin, and scalar spin–spin interactions.

Observation of iodine transitions using the second and third harmonics of a 1.5-μm laser

This paper presents spectroscopic measurements of iodine at 778 nm and 518 nm performed by second and third harmonics of a 1.5-μm diode laser, generated by quasi-phase matching in a periodically poled lithium niobate waveguide. Sub-Doppler spectroscopy by a 780-nm source was also demonstrated, and shows the potential of the system to reach high levels of frequency stability by locking the laser to the iodine transitions. The suggested method significantly improves the number of frequency references available for stabilizing 1550-nm lasers.

Measurements of Pressure-Broadening Coefficients for the F‘ = 3 ← F‘ ‘ = 4 Hyperfine Line of the 2P1/2 ← 2P3/2 Transition in Atomic Iodine

We describe a series of measurements of pressure-broadening coefficients for the F‘ = 3 ← F‘ ‘ = 4 line of the 2P1/2 ← 2P3/2 transition in atomic iodine. This is the optical transition of the chemically pumped atomic iodine laser (COIL), and our results are relevant to a more complete understanding of this important class of high-power lasers. The measurements were made in sealed cells using an argon ion laser to photodissociate molecular iodine and a tunable diode laser to probe directly the atomic transition. We measured broadening coefficients for three bath gases: He, N2, and O2. Full absorption line shapes were recorded as a function of the added bath gas pressure and the following values were obtained at room temperature: (Δν/ΔPHe)T=296K = 3.2 ± 0.3 MHz/Torr, (Δν/ΔPN2)T=296K = 5.5 ± 0.6 MHz/Torr, and (Δν/ΔPO2)T=296K = 5.0 ± 0.5 MHz/Torr; where Δν is the full width at half-maximum. We also measured the temperature dependencies of the He and O2 broadening coefficients over the range 296 K < T < 775 K. We quote the temperature-dependent values as (Δν/ΔPHe)T = (3.2 ± 0.3) × (296/T)0.36 and (Δν/ΔPO2)T = (5.5 ± 0.6) × (296/T)0.70. Comparisons to previous measurements are also discussed.

Vibration dependence of the tensor spin–spin and scalar spin–spin hyperfine interactions by precision measurement of hyperfine structures of ^127I_2 near 532 nm

Hyperfine structures of the R(87)33-0,R(145)37-0, and P(132)36-0 transitions of molecular iodine near 532 nm are measured by observing the heterodyne beat-note signal of two I2-stabilized lasers, whose frequencies are bridged by an optical frequency comb generator. The measured hyperfine splittings are fit to a four-term Hamiltonian, which includes the electric quadrupole, spin–rotation, tensor spin–spin, and scalar spin–spin interactions, with an accuracy of ∼720 Hz. High-accurate hyperfine constants are obtained from this fit. Vibration dependences of the tensor spin–spin and scalar spin–spin hyperfine constants are determined for molecular iodine, for the first time to our knowledge. The observed hyperfine transitions are good optical frequency references in the 532-nm region.

Absolute-frequency measurement of the iodine-based length standard at 514.67 nm

The absolute frequency of the length standard at 514.67 nm based on the molecular iodine (127 I 2) transition of the P(13) 43-0 component a3 is measured using a self-referenced femtosecond optical comb. This frequency-based technique improves measurement precision more than 100 times compared with previous wavelength-based results. Power- and pressure-related frequency shifts have been carefully studied. The measured absolute frequency is 71.8±1.5 kHz higher than the internationally accepted value of 582490603.37±0.15 MHz, adopted by the Comite International des Poids et Mesures (CIPM) in 1997.

Molecular iodine clock.

We demonstrate a simple optical clock based on an optical transition of iodine molecules, providing a frequency stability superior to most rf sources. Combined with a femtosecond-laser-based optical comb to provide the phase coherent clock mechanism linking the optical and microwave spectra, we derive an rf clock signal of comparable stability over an extended period. Measurements suggest the stability ( 5x10(-14) at 1 s) of the cw laser locked on the iodine transition is transferred to every comb component throughout the optical octave bandwidth (from 532 to 1064 nm) with a precision of 3.5x10(-15). Characterization of the performance of the optical clock shows (in-)stability below 3x10(-13) at 1 s (currently limited by the microwave sources), and 4.6x10(-13) over one year.