Abstract:Abstract:We investigate lasing from high-Q, polymeric goblet-type microcavities covered by an organic semiconductor gain layer. We analyze the optical modes in the high-Q cavities using finite element simulations and present a numerical method to determine the cutoff thickness of the gain layer above which the whispering gallery modes are strongly confined in this layer. Fabricated devices show reduced lasing thresholds for increasing gain layer thicknesses, which can be explained by a higher filling factor of… Show more
“…A clear lasing threshold was measured at approximately 50, 20 and 80 nJ of pulse energy for the triangle-, cubic- and hexagon-shaped structures, respectively, by fitting the emission dependence on the pump energy to a bilinear curve. Such threshold energies are comparable to which have been achieved for polymer microlasers relying on usual cavities 7 , 8 , 30 , 31 . Figure 5 Integrated emission intensity as a function of pump energy for ( a ) triangle-, ( b ) cubic- and ( c ) hexagon-shaped microstructures (threshold energies are shown in each corresponding graph).…”
Here we demonstrate resonant random lasing in Rhodamine B-doped polymeric microstructures fabricated by means of femtosecond laser writing via two-photon polymerization. To the best of our knowledge, this is the first demonstration of random lasing action in on-chip microdevices. Their feedback mechanism relies on diffuse reflections at the structure sidewall surfaces, which is known as spatially localized feedback since the scattering centers lie over the edges of the gain medium. By exciting the structures with a pulsed laser at 532 nm, a multimode emission with randomly distributed narrow peaks was observed, in accordance with the random nature of the feedback mechanism. Interestingly, their lasing threshold was found to be on the order of tens of nanojoules, which is comparable to what had been achieved for usual microcavities, thereby demonstrating the potentiality of these devices as solid-state lasers for integrated optics applications.
“…A clear lasing threshold was measured at approximately 50, 20 and 80 nJ of pulse energy for the triangle-, cubic- and hexagon-shaped structures, respectively, by fitting the emission dependence on the pump energy to a bilinear curve. Such threshold energies are comparable to which have been achieved for polymer microlasers relying on usual cavities 7 , 8 , 30 , 31 . Figure 5 Integrated emission intensity as a function of pump energy for ( a ) triangle-, ( b ) cubic- and ( c ) hexagon-shaped microstructures (threshold energies are shown in each corresponding graph).…”
Here we demonstrate resonant random lasing in Rhodamine B-doped polymeric microstructures fabricated by means of femtosecond laser writing via two-photon polymerization. To the best of our knowledge, this is the first demonstration of random lasing action in on-chip microdevices. Their feedback mechanism relies on diffuse reflections at the structure sidewall surfaces, which is known as spatially localized feedback since the scattering centers lie over the edges of the gain medium. By exciting the structures with a pulsed laser at 532 nm, a multimode emission with randomly distributed narrow peaks was observed, in accordance with the random nature of the feedback mechanism. Interestingly, their lasing threshold was found to be on the order of tens of nanojoules, which is comparable to what had been achieved for usual microcavities, thereby demonstrating the potentiality of these devices as solid-state lasers for integrated optics applications.
“…Applications of these devices for single molecule detection were suggested but not demonstrated yet. 189,190 Microdisk resonators are similar to microgoblets, only that the microdisk is flat. Microdisks can reside on pedestals, sit flat on a low-refractive index substrate or be embedded in a low-index mold.…”
Section: Microgoblet and Microdisk Wgm Resonatorsmentioning
Organic dyes have been used as gain medium for lasers since the 1960s, long before the advent of today's organic electronic devices. Organic gain materials are highly attractive for lasing due to their chemical tunability and large stimulated emission cross section. While the traditional dye laser has been largely replaced by solid-state lasers, a number of new and miniaturized organic lasers have emerged that hold great potential for lab-on-chip applications, biointegration, low-cost sensing and related areas, which benefit from the unique properties of organic gain materials. On the fundamental level, these include high exciton binding energy, low refractive index (compared to inorganic semiconductors), and ease of spectral and chemical tuning. On a technological level, mechanical flexibility and compatibility with simple processing techniques such as printing, roll-to-roll, self-assembly, and soft-lithography are most relevant. Here, the authors provide a comprehensive review of the developments in the field over the past decade, discussing recent advances in organic gain materials, which are today often based on solid-state organic semiconductors, as well as optical feedback structures, and device fabrication. Recent efforts toward continuous wave operation and electrical pumping of solid-state organic lasers are reviewed, and new device concepts and emerging applications are summarized.
“…Whispering gallery mode optical cavities have been used in the development of microlaser systems through many different methods, which include utilizing the inherent non-linear characteristics of the cavity or implanting a material within the cavity to serve as the gain material [1][2][3][4][5][6][7][8][9][10][11] . Applications for whispering gallery mode optical resonators range from single virus detection to the creation of frequency combs 12,13 .…”
Due to their long photon lifetimes, ultra high quality factor (Q) silica microcavities form an ideal platform for microlaser development. Previous work verified that these devices exhibit Raman lasing, because the high Q compensates for the low Raman gain of silica. However, only devices with Q>1E8 are able to achieve microwatt thresholds, limiting the application space. One approach for overcoming this barrier is to increase the inherent Raman gain of the material without degrading the optical performance of the device. To address this challenge, we synthesize a series of titanium (Ti) doped silica sol-gels with different concentrations of Ti, including a null. The refractive indices of the coatings are characterized using spectroscopic ellipsometry and increase linearly with the concentration of Ti from 1.44 to 1.51. We apply the sol-gel as a conformal coating on silica toroidal microcavities and characterize the basic cavity properties (Q) and the lasing behavior, including the lasing threshold and the slope efficiency. All measurements are performed in ambient conditions. Although the cavity Q's are modest (5E6), comparable lasing thresholds (microwatt) to higher Q silica devices are achieved because of the reduction in mode volume and the increase in Raman gain due to the presence of the Ti. Additionally, the efficiency of the laser increases with increasing Ti concentration.
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