Jerzy S. Krasinski

Observation of a spectral hole due to population oscillations in a homogeneously broadened optical absorption line

Abstract We have observed a dip in the absorption profile of the homogeneously broadened green absorption band of ruby for frequencies near that of a saturating, cw laser beam. The shape and depth of the hole thus produced have been measured using weak amplitude modulation sidebands as a probe, and are found to be in good agreement with theoretical predictions. These predictions are based on a model that ascribes the origin of the hole to the periodic modulation of the ground state population at the beat frequency between the pump and probe beams. The theory includes the effect of pump depletion. Holes as narrow as 37 Hz (HWHM) have been observed.

Two-photon conical emission

Abstract A two-photon resonantly enhanced four-wave mixing (FWM) process leading to the conical emission of two new frequency components has been observed in atomic sodium vapor. A dye laser tuned close to the 3s → 3d two-photon allowed transition produces broad-band emission near the frequencies of the 3d → 3p and 3p → 3s transitions. This radiation is emitted in the forward direction in the form of cones surrounding the transmitted laser beam. The dependence of the cone angle on the emission wavelength and atomic number density is in excellent agreement with the predictions of a model that ascribes the origin of the conical emission to a phase-matched four-wave mixing process.

Dynamics of homogeneously broadened lasers: higher-order bichromatic states of operation

A theory is presented that describes a series of bichromatic states of an ideal homogeneously broadened laser. These states are produced when the laser is pumped far above threshold so that the intracavity field is strong enough to overcome damping and produce Rabi oscillations of the atomic inversion. The two-frequency laser field is amplitude modulated at a frequency that may be either the Rabi frequency or a subharmonic of it. The theoretical predictions are compared qualitatively with recent experimental results.

Nonlinear optical properties of fluorescein in boric-acid glass

Abstract Fluorescein in boric-acid glass has an extremely low saturation intensity measured in saturated absorption and phase conjugation experiments to be of the order of 10 mW cm 2 . The time evolution of the long-lived luminescence is highly nonexponential, leading to a nonlorentzian spectral hole of width ∼750 millihertz in the absorption profile measured in a pump-probe experiment.

Disk-shaped heat-pipe oven used for lithium excited-state lifetime measurements

A metal-vapor spectroscopic oven based on the heat-pipe principle has been constructed in which the heated stainless steel wicks are mounted on disks spaced closely compared with their radii and in which the window is a glass spacer ring separating the disks and permitting optical access to the active volume. The device has been successfully operated using both sodium and lithium as the working fluid. The lithium 4s2S1/2 and 5s2S1/2 radiative lifetimes were measured with this device, yielding values of 56 ± 1.7 and 99 ± 9 nsec, respectively.

Observation of resonantly enhanced sum-frequency generation involving sodium Rydberg states

A large, dc-electric-field-induced nonlinear optical susceptibility is exploited to produce ultraviolet radiation in the range 2453-2476 A by the process of sum-frequency generation in sodium. The interaction is resonantly enhanced at the first intermediate level by the 3 (2)P(3/2) state and at the second intermediate level by a Rydberg state. Conversion efficiencies of 10(-5) have been obtained; improvement of this value by a factor of 10(3) should be possible.

Continuously tunable sum-frequency generation involving sodium Rydberg states

Broadly tunable sum-frequency generation has been observed in a vapor of atomic sodium in the presence of a dc electric field. This field induces a chi^{(2)} nonlinearity which is resonantly enhanced when the sum frequency corresponds to the energy separation between the ground state and an atomic Rydberg state. In a vapor of number density 4 times 10^{14} cm-3, we obtain an energy conversion efficiency as large as 3 times 10^{-4} and a chi^{(2)} as large as 1.2 times 10^{-8} ESU. We have also observed sum-frequency generation in the absence of an applied dc field, and we relate these observations to mechanisms that have been proposed to explain this effect.

Intrinsic Instabilities in Homogeneously Broadened Lasers

We have studied the behavior of a cw homogeneously broadened ring dye laser operading far above threshold. We have found that although the laser operates in a single mode when it is near threshold, it is intrinsically unstable when pumped far above threshold. The onset of the instability is characterized by an abrupt increase in the power circulating in the cavity. In addition, the spectral output of the laser changes. Below the onset of the instability lasing occurs at gain center, while above this threshold, lasing occurs simultaneously at two frequencies symmetrically displaced from gain center. The splitting of the two lasing frequencies follows a parabolic power dependence. At still greater pump powers, higher order splittings and instabilities were observed. These instabilities exhibit hysteresis about the critical pump powers.

Continuously tunable sum‐frequency generation involving Rydberg states

Extremely large values of the second‐order nonlinear susceptibility have been demonstrated in a system involving Rydberg states. The applicability of this technique to the extreme ultraviolet is discussed.