Co
                  2+
              :
              ZnS
           and Co2+:ZnSe saturable absorber <i>Q</i> switches

Tsai, Tsuen‐Chiuan; Birnbaum, Milton

doi:10.1063/1.371821

Cited by 74 publications

(46 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…TC Co 2+ ions in ZnSe and ZnS crystals are also know as PS for Er lasers. Pulses of duration up to 10 nsec and energy up to 10 mJ were obtained using PS based on Co 2+ :ZnSe in a glass Er laser with lamp pumping [120,126,127]. Glass Er laser emission characteristics with PS of Co 2+ :ZnSe were investigated where the generation occurred in TEM mn -mode with various m and n values [244].…”

Section: Ermentioning

confidence: 99%

Saturable absorbers based on tetrahedrally coordinated transition-metal ions in crystals (Review)

Malyarevich

Yumashev

2009

J Appl Spectrosc

View full text Add to dashboard Cite

Published data on spectroscopic characteristics of saturable absorbers based on crystals doped with tetrahedrally coordinated transition-metal ions (Cr 2+ , Cr 4+ , Cr 5+ , V 3+ , Cr 2+ , Fe 2+ ) in addition to their use as passive Q-switches for solid-state lasers emitting in the visible and near-infrared regions are reviewed.Introduction. The use of saturable absorbers (SA) as passive Q-switches (PS) in solid-state lasers is an effective method for generating nanosecond and subnanosecond light pulses. This method differs favorably from active control of laser cavity gain by the lack of mechanical perturbations of the optical devices, additional sources of power supply, and external electrical control circuits. This simplifies the construction and operation of the laser and reduces its cost. Compact solid-state mini-lasers and ultra-small lasers (so-called microchip lasers) can be fabricated if PS are used.A SA is an optical material for which the transmission increases with increasing power density of the incident radiation. The SA should satisfy several requirements in order to be used as a PS. First of all this applies to SA characteristics at the laser operating wavelength such as absorption saturation energy density, coefficient of residual absorption in the fully bleached state, bleaching rise and fall time, and optical destruction threshold. The requirements for their absolute values depend on the spectroscopic properties of the lasing medium (LM) and the laser cavity parameters.In most instances with certain exceptions, SA based on tetrahedrally coordinated (TC) transition-metal ions of the iron group have bleaching relaxation times that are longer than the generation time of the laser pulses obtained using them. Such SA are usually called slowly relaxing. Relaxation processes leading to a restoration of their initial absorption can be ignored in analyzing their operation in a laser. In the simplest instance (if a four-level diagram is used for the spectroscopic model of the SA), the criterion for SA functioning as a PS is written [1-8]:

show abstract

Section: Ermentioning

confidence: 99%

Saturable absorbers based on tetrahedrally coordinated transition-metal ions in crystals (Review)

Malyarevich

Yumashev

2009

J Appl Spectrosc

View full text Add to dashboard Cite

show abstract

“…According to (19), the losses α ap (F P = I P /hν, discussed in Section 1.2.2 (formula (10)), are described by the expression α ap (…”

Section: Continuous Pumpingmentioning

confidence: 99%

“…Formula (19) shows that saturation of a fast relaxing absorber is determined by the intensity of the radiation I in . Such a saturable absorber is characterized by intensity transmission T, and the nonlinearity parameter describing its bleaching is the absorption saturation intensity I sa = hν/γ a σ a τ a .…”

Section: Continuous Pumpingmentioning

confidence: 99%

Nonlinear bleachable media for the near IR range based on lead chalcogenide quantum dots (review)

Malyarevich

Yumashev

2007

J Appl Spectrosc

View full text Add to dashboard Cite

We present a review of results from study of the nonlinear optical properties and relaxation processes in lead chalcogenide quantum dots embedded in glass matrices of various compositions, and also designs for bleachable media based on these materials for Q-switched and mode-locked solid-state lasers in the near IR range. We consider the conditions which should be satisfied by the spectroscopic characteristics of saturable absorbers for realization of passive Q-switching and mode-locking in solid-state lasers.Introduction. Nanometer-sized semiconductor particles (quantum dots (QDs)) are among systems with pronounced quantum effects, caused by confinement of the motion of the electrons and holes by the finite dimensions of the nanoparticle [1][2][3][4]. If the dimensions of the quantum dot are comparable with the Bohr exciton radius in a bulk semiconductor, then we observe a shift of the optical absorption edge of the quantum dot toward higher energies relative to the bandgap width of the bulk semiconductor. To a first approximation, the magnitude of this shift is inversely proportional to the square of the quantum dot radius. Furthermore, the quantum dot absorption spectrum has structure: individual bands appear due to splitting of the valence band and the conduction band into individual energy levels, between which there are certain optical transitions with selection rules. As a result, it becomes possible to monotonically shift the quantum dot absorption edge toward shorter wavelengths, starting from the wavelength corresponding to the bandgap width of the semiconductor compound. Thus semiconductors with a relatively narrow bandgap, in particular lead chalcogenides, make it possible to shift the absorption edge within practically the entire near IR region of the spectrum, by varying the size of the quantum dot. The effect of an increase in transmission (bleaching) in the region of the quantum dot absorption bands upon resonant interaction with an intense light beam allows us to use quantum dots as bleachable media (saturable absorbers) to control the temporal parameters of emission from laser systems.Bleachable media, using the effect of saturation of optical absorption, have become widely used to obtain high-power light pulses of short/ultrashort duration in Q-switched and mode-locked solid-state lasers emitting in the near IR region of the spectrum. Using such laser pulses provides broad possibilities for treatment of materials, information transfer, ranging, monitoring for occurrence of industrial processes, environmental monitoring, biomedical diagnostics, laser surgery and therapy, and also in science (especially in nonlinear optics and laser spectroscopy). Practical application requires laser systems that operate reliably, are easy to service, compact, and low-cost. A solid-state bleachable medium as a component of a laser system sufficiently meets the indicated requirements. This component is usually a plate or film (on a substrate) made from a solid material, and does not require any external mechanical...

show abstract

“…The spectroscopic characteristics presented for the active medium and the passive gate, their geometric dimensions, and also the specified cavity parameters were used to model the operation of the laser and to determine the optimal value of the reflection coefficient for the output mirror of the cavity, with the aim of ensuring the best energy and temporal parameters for the radiation pulse. The model used is based on a system of kinetic equations, and takes into account losses to re-absorption of the laser radiation in the active medium and ESA losses in the saturable absorber [13]:…”

mentioning

confidence: 99%

Passive Q-switching of erbium glass laser by magnesium aluminosilicate sitall with cobalt ions

et al. 2007

View full text Add to dashboard Cite

We have studied the radiation output parameters for an erbium glass laser, lasing at a wavelength of 1.54 µm, with passive Q-switching by means of a cobalt-containing magnesium aluminosilicate sitall compared with a saturable absorber based on a magnesium aluminum spinel crystal with cobalt ions. We have shown that the output characteristics of the laser emission when using sitall are not inferior to the analogous characteristics of a laser based on a spinel crystal, and are practically independent of the temperature of the saturable absorber in the range 0 o C-80 o C. The duration (energy) of the output pulses was 70 nsec (~4 mJ), the energy dispersion of the radiation pulse relative to the average value was no greater than 3%, the beam divergence was 2.8 mrad, the laser beam quality factor was M 2 = 1.2.Key words: Q-switching, erbium glass laser, Co 2+ ion, magnesium aluminum spinel, aluminosilicate sitall.Introduction. In recent years, considerable attention has been focused on designing laser radiation sources in the 1.5 µm region. Radiation with this wavelength falls within the transparency range of the atmosphere and is eyesafe, which means that the prospects are good for using these lasers in range finders, target acquisition systems, systems for remote probing of the atmosphere, data transmission and processing. This is why it is important to develop a stable and efficient source of laser radiation that lases in this spectral range.For the applications indicated above, we need nanosecond radiation pulses with high peak power. Such pulses can be obtained by operating the laser in passively Q-switched mode. Today the most efficient passive gate for erbium glass lasers, lasing at a wavelength of 1.54 µm, is a magnesium aluminum spinel containing divalent cobalt ions (Co 2+ :MgAl 2 O 4 ) [1][2][3][4]. In this material, the Co 2+ ions occupy positions with tetrahedral coordination and have a large ground state absorption (GSA) cross section (σ GSA ≈ (3-5)⋅10 -19 cm 2 ), a rather long bleaching relaxation time (τ = 300-400 nsec), and low excited state absorption (ESA) (σ ESA /σ GSA < 0.05) [1,4]. At the same time, it has been demonstrated [5][6][7] that materials in the form of transparent glassceramic (sitall) containing divalent cobalt ions can be used as passive gates for lasers in the spectral range 1.3-1.6 µm. It has been established that during synthesis of aluminosilicate sitall, a microcrystalline spinel phase is formed in it where the Co 2+ ions are found in tetrahedral coordination. This provides it with the optical characteristics needed for laser applications [8][9][10]. In particular, in the 1.5 µm region, sitalls with Co 2+ ions have ground state absorption and excited state absorption (GSA and ESA) cross sec-

show abstract

Co 2+ : ZnS and Co2+:ZnSe saturable absorber Q switches

Cited by 74 publications

References 7 publications

Saturable absorbers based on tetrahedrally coordinated transition-metal ions in crystals (Review)

Saturable absorbers based on tetrahedrally coordinated transition-metal ions in crystals (Review)

Nonlinear bleachable media for the near IR range based on lead chalcogenide quantum dots (review)

Passive Q-switching of erbium glass laser by magnesium aluminosilicate sitall with cobalt ions

Contact Info

Product

Resources

About