We demonstrate a Doppler-free spectroscopic method that we test on 87 Rb and 85 Rb vapor. By using a magnetic field to induce a dichroism on the sample, we generate a dispersive signal with low background, which allows us to lock a diode laser even on small spectroscopic features. We elaborate the advantages of this simple and easy method by comparing it to other methods.

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Doppler-free spectroscopy using magnetically induced dichroism of atomic vapor: a new scheme for laser frequency locking

A method is presented for obtaining sub-Doppler and subnatural narrowing and increased absorption of a spectral line. The ultranarrow spectral line is confined between two closely spaced electromagnetically induced transparency windows in a nearly degenerate tripod atomic system formed by an ${F}_{g}=1\ensuremath{\rightarrow}{F}_{e}=0$ transition, split by a magnetic field. The system is driven by a $\ensuremath{\sigma}$-polarized pump and probed by a tunable $\ensuremath{\pi}$-polarized laser. It can be used to measure small magnetic fields and also as a magneto-optic switch.

Sub-Doppler and subnatural narrowing of an absorption line induced by interacting dark resonances in a tripod system

Using the density matrix formalism, we prove the existence of the periodic steady state for an arbitrary periodically driven system described by linear dynamic equations. This state has the same period as the modulated external influence, and it is realized as an asymptotic solution $(t\ensuremath{\rightarrow}+\ensuremath{\infty})$ due to relaxation processes. The presented derivation simultaneously contains a simple and effective computational algorithm (without using either the Floquet or Fourier formalisms), which automatically guarantees a full account of all frequency components. As a particular example, for three-level $\mathrm{\ensuremath{\Lambda}}$ system we calculate the line shape and field-induced shift of the dark resonance formed by the field with a periodically modulated phase. Also we have analytically solved a basic theoretical problem of the direct frequency comb spectroscopy, when the two-level system is driven by the periodic sequence of rectangular pulses. In this case, the radical dependence of the spectroscopy line shape on pulse area is found. Moreover, the existence of quasiforbidden spectroscopic zones, in which the Ramsey fringes are significantly reduced, is predicted. Our results have a wide area of applications in laser physics, spectroscopy, atomic clocks, and magnetometry. Also they can be useful for any area of quantum physics where periodically driven systems are considered.

Dynamic steady state of periodically driven quantum systems

We analyzed the spectroscopic performance of a difference-frequency source that utilizes a 5-W Yb-fiber amplifier for the “signal” radiation in order to increase the “idler” power generated around 4.3 μm. The amplifier is seeded by a monolithic-cavity Nd:YAG laser at 1064 nm. The intensity noise spectral density of the “idler” radiation was characterized. Cavity-enhanced saturated-absorption spectroscopy was also performed to test the frequency resolution. In particular, we observed the Lamb-dip spectrum of the ro-vibrational (0000-0001)R(0)transition of 17O12C16O in natural abundance. To our knowledge, this is the first observation of that transition by the Lamb-dip technique.

Power-boosted difference-frequency source for high-resolution infrared spectroscopy

This paper describes the experimental investigation of stimulated Raman scattering obtained from a multimode fiber. 10 orders of stimulated Stokes scattering of wavelengths in the 546–702 nm region were obtained from a 480m multimode, low-loss, graded-index quartz fiber pumped by a 532 nm frequency-doubled YAG-Nd laser beam with a pulse duration of 7 ns, output power of 0.7 MW and repetition rates of 5 and 10 pps.

Stimulated raman scattering up to 10 orders in an optical fiber

The three basic methods of linear laser spectroscopy are reviewed: absorption, opto-acoustic, and fluorescence spectroscopy The characteristics of each method and their areas of application are presented and compared

Laser spectroscopy: 3. Linear laser spectroscopy

This article discusses the recent achievements, new possibilities, and prospects for the selective detection of ultra-low concentrations of atoms and molecules by laser radiation The first part of the article considers methods of detecting atoms The far more difficult case of selective detection of polyatomic molecules is the subject of the second part of the article

Laser spectroscopy: 6. Selective detection of ultra-low concentrations of atoms and molecules

Multiphoton and multistep spectroscopy of atoms and molecules is a rapidly developing branch of laser spectroscopy which relies almost exclusively on the application of tunable lasers. This article reviews the different techniques which have been developed.

Laser spectroscopy: 7. Multiphoton and multistep methods

Picosecond laser spectroscopy is a rapidly developing field, the applications of which extend to the adjacent subjects of chemistry and biology. Here, the various methods and areas of application are classified and compared. Some experiments and results are mentioned for illustration.

Laser spectroscopy 8. Picosecond processes

This concluding article in the series discusses the prospects of realizing the ultimate parameters — spectral resolving power and sensitivity — and some fields of application — nuclear physics, chemical kinetics and molecular physics, quantum metrology — of laser spectroscopy.

V.S. Letokhov

Papers

Laser spectroscopy: 3. Linear laser spectroscopy

Laser spectroscopy: 6. Selective detection of ultra-low concentrations of atoms and molecules

Laser spectroscopy: 7. Multiphoton and multistep methods

Laser spectroscopy 8. Picosecond processes

Laser spectroscopy 9. Prospects and applications