Fig 4 - uploaded by Randy Knize
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Ring cavity Cs laser setup: M1, M2, M3 and M4-cavity mirrors, OD-optical diode, FP-Fabry-Perot etalon, PT-piezo transducer, Cell-Cs vapor cell in oven, L-focusing lens.
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Diode pumped alkali vapor lasers developed during the last several years have the potential to achieve high power. Efficient operation of Rubidium, Cesium and Potassium lasers has been demonstrated. Laser slope efficiencies higher than 80% have been achieved. A diode laser pumping can provide high overall efficiency of these devices. A diode pumped...
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... It is well known that in the presence of high pressure buffer gas, there is rapid inter-mixing and dephasing of atoms in the 5P 3/2 and the 5P 1/2 states of alkali metals [13][14][15][16][17]. For concreteness, we restrict our discussion to the case where the buffer gas used is Ethane, and the alkali atom of interest is 85 Rb. ...
Modulators using atomic systems are often limited in speed by the rate of spontaneous emission. One approach for overcoming this limit is to make use of a buffer gas such as Ethane, which causes rapid fine structure mixing of the P1/2 and P3/2 states, and broadens the absorption spectra of the D1 and D2 lines in alkali atoms. Employing this effect, we show that one can achieve high speed modulation using ladder transitions in Rubidium. We demonstrate a 100-fold increase, due to the addition of the buffer gas, in the modulation bandwidth using the 5S-5P-5D cascade system. The observed bandwidth of ~200 MHz is within a factor of 2.5 of the upper bound of ~0.51 GHz for the system used, and is limited by various practical constraints in our experiment. We also present numerical simulations for the system and predict that a much higher modulation speed should be achievable under suitable conditions. In combination with a tapered nano fiber or a SiN waveguide, it has the potential to be used for high-speed, low-power all-optical modulation.
... The HL can be increased very significantly by adding a buffer gas, such as 4 He. In a series of studies carried out in the context of the development of diode pumped alkali lasers (DPALs) [26], it has been shown that the atoms excited to the 5P 3/2 state relaxes very rapidly to the 5P 1/2 state. This process increases the HL for the pump transition significantly. ...
We demonstrate a high-efficiency optical modulator at ~1323 nm using the quantum Zeno effect in a ladder transition in a Rb vapor cell. The lower leg of the transitions represents the control beam while the upper leg of the transitions represents the signal beam. The cross-modulation of the signal beam transmission is observed as the control beam is intensity modulated, and is explained in terms of the quantum Zeno effect. We observe a modulation depth of near 100% at frequencies up to 1MHz and demonstrate modulation at speeds up to 75 MHz, with a 3 dB bandwidth of about 5 MHz, limited by the homogeneous linewidth of the intermediate state. We also describe how much higher modulation speeds could be realized by using a buffer gas to broaden the transitions. We identify and explain the special conditions needed for optimizing the modulation efficiency. Numerical simulations of modulation at ~1GHz are presented. The maximum modulation speed is found to scale with the pressure-broadened linewidth of the intermediate state, so that much higher speeds should be attainable.
... B EING a new class of laser device, Diode pumped alkali vapor lasers-DPALs have both the advantages of gas lasers and solid lasers, which possess some desirable features such as smaller quantum defect, lower thermal effect and higher efficiency as compared to other high power lasers [1,2]. DPALs can output high power lasers in near infrared spectrum with higher beam quality, and have extensive potential applications in laser cooling, directional energy transmission, material processing, atmospheric propagation and so on [3,4]. They can be an alternative to the most developed and successful high power laser systems and even exceed other lasers in many aspects [5]. ...
... The HL can be increased very significantly by adding a buffer gas, such as 4 He. In a series of studies carried out in the context of the development of diode pumped alkali lasers (DPALs) [27], it has been shown that the atoms excited to the 5P 3/2 state relaxes very rapidly to the 5P 1/2 state. The rate of relaxation from the 5P 1/2 state to the ground state can be augmented by adding an auxiliary, strong beam that would be turned on at the same time as the pump is turned off, and turned off before turning on the pump again. ...
We demonstrate an ultra-low light level optical modulator using a tapered nano fiber embedded in a hot rubidium vapor. The control and signal beams are co-propagating but orthogonally polarized, leading to a degenerate V-system involving coherent superpositions of Zeeman sublevels. The modulation is due primarily to the quantum Zeno effect for the signal beam induced by the control beam. For a control power of 40 nW and a signal power of 100 pW, we observe near 100% modulation. The ultra-low power level needed for the modulation is due to a combination of the Zeno effect and the extreme field localization in the evanescent field around the taper.
... True diode-pumped DPALs have also been developed for Cs and Rb in static gain-medium cells with output powers and slope efficiencies, respectively, as high as 10W and 68% (Cs) and 17W and 53% (Rb). 4,5 In each of these experiments the gain medium was static, and waste heat removal from the lasing volume occurred through free convection. Efforts to further increase DPAL average output power have retained static gain media but resort to geometries in which at least one high thermal-conductivity wall is placed close to the pumped active laser volume, as in a circular capillary or a planar waveguide. ...
A new generation of laser weapons are being introduced in the market following new plans for laser weapons development. The Defense Advanced Research Projects Agency's (DARPA) Space Laser Triad include construction of a 5 MW hydrogen-fluoride (HF) chemical laser on the ground, Alpha, to show feasibility of orbiting laser battle stations to block a Soviet nuclear attack. The Missile Defense Agency's (MDA) fiscal 2011 budget proposal identifies diode-pumped alkali lasers as the leading candidate for missile defense. Performance testing and engineering of two Joint High-Power Solid-State Laser (JHPSSL) demonstrations that have diode-pumped slab geometries at the forefront of battlefield laser development is expected shortly. In an another development, the US Navy is designing a 100 kW class free-electron laser weapon system for use on ships, in the hope that a free-electron laser could identify low-value targets at lower cost than expensive missiles.
We show theoretical simulations of how a high speed optical modulator can be realized at a telecommunication wavelength using the buffer gas induced relaxation in a ladder transition in Rb atoms at room temperature.
We report on the experimental progress of an ultra-low power, high speed optical modulator in a tapered nano fiber system using buffer gas induced line broadening of ladder transitions in Rb atoms.
The diode pumped alkali vapor lasers are significantly beneficent from the developing of a new generation of highpower laser diode sources. The latest achievements in the technology of photo-thermo-refractive volume Bragg gratings opened new opportunities for the design and fabrication of compact external cavity laser diodes and bars with reflecting volume Bragg gratings as output couplers. A new developed fiber coupled 250W source consists from 7 channels of independently stabilized commercially available LD bars with standard AR-coatings at output facets. Using a specially designed reflecting volume Bragg grating, we demonstrated spectral narrowing of a single LD bar spectrum by over two orders of magnitude down to 16-18 pm at 780 nm wavelength. The volume Bragg laser bar output power exceeded 88% of that for the free-running laser bar. The spectral position of each LD precise tuning is made by means of a special method of temperature stabilization of an output volume Bragg coupler. Overall spectral width for whole system was less than 20 pm (
The diode pumped alkali vapor lasers operating at subatmospheric pressure require developing of a new generation of high-power laser diode sources with about 10 GHz wide emission spectrum. The latest achievements in the technology of volume Bragg gratings (VBGs) recorded in photo-thermo-refractive glass opened new opportunities for the design and fabrication of compact external cavity laser diodes, diode bars and stacks with reflecting VBGs as output couplers. We present a diode laser system providing up to 250 W output power and emission spectral width of 20 pm (FWHM) at the wavelength of 780 nm. The stability and position of an emission wavelength is determined by the resonant wavelength of a VBG which is controlled by temperature. Stability of an emitting wavelength is within 5 pm. Thermal tuning of the wavelength provides maximum overlapping of emitting line with absorption spectrum of a Rb (rubidium)- cell. The designed system consists of 7 modules tuned to the same wavelength corresponding to D2 spectral line of Rb87 or Rb85 and coupled to a single output fiber. Analogous systems could be used for other Rb isotopes spectral lines as well as for lasers based on other alkali metal vapors (Cs and K) or any agents with narrow absorption lines.
