Blue surface-emitting distributed feedback lasers based on TPD-doped films

Calzado, Eva M.; Villalvilla, José M.; Boj, Pedro G.; Quintana, José A.; Postigo, P. A.; Díaz-García, María A.

doi:10.1364/ao.49.000463

Cited by 27 publications

(28 citation statements)

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“…Some preliminary discussions at this respect can be found elsewhere. 17,22 We also investigated the effect of changing the size of the excitation beam on the operational lifetime of the devices. As expected, when excitation was performed with spot areas larger than A crit , so the energy and power density thresholds were the same, similar lifetimes (considering that the experimental errors is around 10%) were obtained.…”

Section: -mentioning

confidence: 99%

Influence of the excitation area on the thresholds of organic second-order distributed feedback lasers

Calzado

Villalvilla

Boj

et al. 2012

Applied Physics Letters

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It is shown that the optical pump power (or energy) density thresholds required to obtain lasing from organic second-order distributed feedback lasers, increase when the excitation area (A) is smaller than a certain value (A crit ). So, in order to obtain the minimum possible thresholds and to ensure that they constitute adequate quantities for comparison purposes, the condition A > A crit should be fulfilled. Results also indicate that when A < A crit (A crit $ 0.1 mm 2 for the devices studied here), the operational device lifetime, which depends mainly on the pump power (or energy) density, becomes drastically reduced. 1,2 The interest in OSLs increased with the discovery of stimulated emission in optically pumped semiconducting polymer films, 3,4 since they opened the possibility of using electrical excitation. The goal of obtaining laser diodes was initially the main motivation to decrease the laser thresholds of OSLs, so many works focused in improving the active materials and the resonators. Although diode lasers have not been demonstrated yet, thanks to all these efforts, laser thresholds have been decreased so much that today it is possible to pump with cheap inorganic diode lasers 1,5 and even with light emitting diodes.6 Therefore, these low-cost and compact optically pumped lasers are by themselves useful for applications. 1,2Among the various types of OSLs reported in the literature, distributed feedback (DFB) lasers have been particularly successful.1,2 So today they are being used to develop applications in the fields of telecommunications, 2 biosensing, and chemical sensing. 7,8 In DFB lasers, the active material is deposited as a thin film over an appropriate substrate so it constitutes a waveguide. Feedback is achieved by the incorporation of periodic nanostructures (obtained by modulating either the refractive index or the gain) that Bragg-scatter the light, thus, avoiding the need of good-quality end facets. In a one-dimensional (1D) DFB laser, the wavelength that satisfies the Bragg condition (k Bragg ) given bywhere m is the order of diffraction, n eff is the effective refractive index of the waveguide, and K is the grating period, constitutes the resonant wavelength in the cavity, which will then be diffracted in the grating in different directions.For second-order DFBs (m ¼ 2 in Eq. (1)), light is coupled out of the film in a direction perpendicular to the waveguide film, by first-order diffraction. DFB resonators can be easily integrated into planar organic waveguides, which is a clear advantage from the fabrication point of view, as compared to other types of laser cavities. In general, OSLs demand very intense pumping conditions due to the short photoluminescence (PL) lifetimes of the active materials (typically 1 ns in the case of fluorescent materials). So, excitation is performed by tightly focusing the pump beam through the gain medium provided by a pulsed laser source. Many of the milestones in achieving low thresholds (expressed as energy per pulse) reported in the literature have...

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Section: -mentioning

confidence: 99%

Influence of the excitation area on the thresholds of organic second-order distributed feedback lasers

Calzado

Villalvilla

Boj

et al. 2012

Applied Physics Letters

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“…Despite the limited amount of information regarding the film thickness dependence of the ASE properties on waveguides, there have been numerous reports investigating the influence of this parameter in the context of organic DFB lasers [13,[18][19][20][21][22]. This is because varying h constitutes the simplest way to tune the emission wavelength (λ DFB ) of the devices, tunability being one of the most attracting properties of organic materials as laser active media.…”

Section: Introductionmentioning

confidence: 99%

“…The available tuning range is limited by the gain spectral width and at lower wavelengths by the overlap with the absorption spectrum. Consequently, in the literature in which the influence of h on the DFB emission threshold has been analyzed, results have been explained in terms of the proximity of the emission wavelength to the maximum of the gain spectrum [13,[18][19][20][21][22]. In some cases, it was suggested that some other parameters, such as the confinement of the waveguide mode [13,18] or the presence of competing higher order modes [19], could play a role.…”

Section: Introductionmentioning

confidence: 99%

Thickness dependence of amplified spontaneous emission in low-absorbing organic waveguides

et al. 2012

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The effect of varying film thickness (h) on the amplified spontaneous emission (ASE) properties of 0.5 wt.% perylenediimide-doped polystyrene waveguides is reported. The threshold dependence on h, not previously investigated in detail, is analyzed in terms of the film absorption and photoluminescence, the confinement of the fundamental waveguide mode (TE 0 ), and the presence of high-order modes. For h < 400 nm and down to 150 nm, the ASE wavelength blueshifts, while the linewidth and threshold increase. The detrimental ASE operation in very thin films is due to the low absorption as well as to the poor confinement of the TE 0 mode.

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“…λ max = 372 nm [19]. The pattern recorded is obtained by the interference of the direct beam (5 cm diameter) and the reflected beam in a mirror attached with a 90° angle to the sample holder (a scheme of the setup can be found in [4]). The light intensity pattern was uniform over the whole sample area.…”

Section: Experimental Techniquesmentioning

confidence: 99%

“…In the context of DFB lasers with active materials in the form of organic waveguide films, the most common geometry consists in a surface-relief grating engraved on top of a conventional substrate, such as glass or SiO 2 , over which the organic active film is deposited [2][3][4][5]. Typically, gratings are recorded over an appropriate resist with EBL, NIL or HL, and then transferred to the substrate by ion-beam etching.…”

Section: Introductionmentioning

confidence: 99%

Distributed feedback lasers based on dichromated poly(vinyl alcohol) reusable surface-relief gratings

Ramírez¹,

Villalvilla²,

Quintana³

et al. 2014

Opt. Mater. Express

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A simple, low-cost and versatile holographic method to produce reusable surface-relief gratings on dichromated poly(vinyl alcohol) (DCPVA) films, with periods Λ ≥ 270 nm and modulation depths up to 300 nm, is reported. DCPVA presents processing advantages with respect to other photoresists, such as dichromated gelatine, i.e. higher light sensitivity, simpler fabrication process and better batch to batch reproducibility. The successful use of these DCPVA relief gratings as distributed feedback (DFB) laser resonators is demonstrated. Second-order DFB devices emitting in the wavelength range 577-614 nm have been easily prepared by coating a dye-doped polymer film on top of the resonators.

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Blue surface-emitting distributed feedback lasers based on TPD-doped films

Cited by 27 publications

References 50 publications

Influence of the excitation area on the thresholds of organic second-order distributed feedback lasers

Influence of the excitation area on the thresholds of organic second-order distributed feedback lasers

Thickness dependence of amplified spontaneous emission in low-absorbing organic waveguides

Distributed feedback lasers based on dichromated poly(vinyl alcohol) reusable surface-relief gratings

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