Browsing by Subject "Microlaser"

Now showing 1 - 3 of 3

Open Access
Robust whispering-gallery-mode microbubble lasers from colloidal quantum dots
(American Chemical Society, 2017) Wang Y.; Ta, V. D.; Leck K.S.; Tan, B. H. I.; Wang, Z.; He T.; Ohl, C.-D.; Demir, Hilmi Volkan; Sun, H.
Microlasers hold great promise for the development of photonics and optoelectronics. Among the discovered optical gain materials, colloidal quantum dots (CQDs) have been recognized as the most appealing candidate due to the facile emission tunability and solution processability. However, to date, it is still challenging to develop CQD-based microlasers with low cost yet high performance. Moreover, the poor long-term stability of CQDs remains to be the most critical issue, which may block their laser aspirations. Herein, we developed a unique but generic approach to forming a novel type of a whispering-gallery-mode (WGM) microbubble laser from the hybrid CQD/poly(methyl methacrylate) (PMMA) nanocomposites. The formation mechanism of the microbubbles was unraveled by recording the drying process of the nanocomposite droplets. Interestingly, these microbubbles naturally serve as the high-quality WGM laser resonators. By simply changing the CQDs, the lasing emission can be tuned across the whole visible spectral range. Importantly, these microbubble lasers exhibit unprecedented long-term stability (over one year), sufficient for practical applications. As a proof-of-concept, the potential of water vapor sensing was demonstrated. Our results represent a significant advance in microlasers based on the advantageous CQDs and may offer new possibilities for photonics and optoelectronics.
Open Access
Self-resonant microlasers of colloidal quantum wells constructed by direct deep patterning
(American Chemical Society, 2021-06-09) Gheshlaghi, Negar; Foroutan-Barenji, Sina; Erdem, Onur; Altintas, Yemliha; Shabani, Farzan; Humayun, Muhammad Hamza; Demir, Hilmi Volkan
Here, the first account of self-resonant fully colloidal μ-lasers made from colloidal quantum well (CQW) solution is reported. A deep patterning technique is developed to fabricate well-defined high aspect-ratio on-chip CQW resonators made of grating waveguides and in-plane reflectors. The fabricated waveguide-coupled laser, enabling tight optical confinement, assures in-plane lasing. CQWs of the patterned layers are closed-packed with sharp edges and residual-free lifted-off surfaces. Additionally, the method is successfully applied to various nanoparticles including colloidal quantum dots and metal nanoparticles. It is observed that the patterning process does not affect the nanocrystals (NCs) immobilized in the attained patterns and the different physical and chemical properties of the NCs remain pristine. Thanks to the deep patterning capability of the proposed method, patterns of NCs with subwavelength lateral feature sizes and micron-scale heights can possibly be fabricated in high aspect ratios.
Open Access
Wavelength-scale lithographic vertical-cavity surface-emitting laser (LI-VCSEL): Design, fabrication and optical characterization
(2021-05) Madigawa, Abdulmalik Abdulkadir
Vertical-cavity surface-emitting lasers (VCSEL) are the ideal light sources for optical data communication and 3D sensing due to their small size, low power consumption, high-speed modulation, and low cost. The key to meeting the ever-increasing demand for higher eﬃciency and modulation devices is scaling down the cavities to near- or sub-wavelength sizes. The current state-of-the-art commercial oxide-VCSEL technology has been very successful for micro-scale cavity diameters (>3 µm), but its processing approach is not appropriate for further miniatur-ization. Improvement in the performance of oxide-VCSELs can be achieved with smaller oxide aperture diameters. However, the high thermal resistance induced by the oxide layer signiﬁcantly degrades the device performance, especially for the smaller sizes, making this method unreliable for scaling. In this work, we investigated a lithographically deﬁned VCSEL (Li-VCSEL) method in which the transverse photonic and electrical conﬁnement can be enabled by epitaxial growth and lithography. Transverse optical conﬁnement is achieved by introducing an intracavity phase-shifting mesa that provides the conﬁnement by index guiding. Numerical simulation results show high-quality factors even for submicron sizes, which is promising for the realization of submicron size single emitter and high-density array lasers. The fabrication steps include the epitaxial growth of the bottom semiconductor DBR and the cavity, deﬁning the phase-shifting mesa us-ing optical lithographic processes, and the deposition of the top dielectric DBR using thin ﬁlm deposition techniques. We demonstrated room-temperature lasing around 980 nm from Li-VCSELs with mesa diameters ranging from 0.75 µm to 2.0 µm under continuous-wave optical pumping and presented detailed charac-terization of these devices. The results represent a signiﬁcant step towards the realization of electrically pumped small-size lasers for practical optoelectronics applications.