Folding flexible co-extruded all-polymer multilayer distributed feedback films to control lasing

Abstract

We report on improved gain and spectral control in co-extruded all-polymer multilayer distributed feedback (DFB) lasers achieved by folding and deliberate modification of the center "defect" layer. Because DFB laser gain is greater at spectral defects inside the reflection band than at the band edges, manipulation of structural defects can be used to alter spectral defects and thereby tune the output wavelength and improve laser efficiency. By experimentally terracing the layer that becomes the center of the fold, we tuned the lasing wavelength across the reflection stop-band (∼25 nm) in controllable, discrete steps. The increased density of states associated with the defect resulted in a lower lasing threshold and, typically, a 3- to 6-fold increase in lasing efficiency over non-folded samples.

Melt‐processed polymer multilayer distributed feedback lasers: Progress and prospects

“…Thus, it is expected (as in Fig. ) that a defect binary DFB laser is optimized by having the gain medium in the lower refractive index material, with a doubled layer of low index material at the center of the stack …”

Structure and symmetry in coherent perfect polarization rotation

“…4 (adapted from Ref. [37]). For example, controlling for overall gain, the folded distributed-feedback structure with the lowest lasing threshold (as inferred from the largest gain in the figure) is that which has the gain medium in the low-index material and is folded on the low-index layer.…”

Thermo-spectral properties of plastic lasers

“…Furthermore, the initial spectral location of the defect in the reflection band depends on the folded layer's (defect center layer's) optical thickness as compared to the average optical thickness of all other layers in the stack. 5,17,18 Also, the choice of the material used as the center defect layer affects the rate of change of the center defect layer's optical thickness relative to the rate of change in the optical thickness of the average layer for systems with bilayers composed of two separate materials with mismatched thermal properties. Therefore, the thermo-emission wavelength coefficient in defect DFB lasers depends on the shift per • C of the reflection band, the initial spectral location of the defect with respect to the band edges, and which bilayer material is used for the center defect layer.…”

“…1, 2 These polymer lasers can be made at low-cost 3 and with broad tunability. [4][5][6] In this paper, we discuss the parameters that affect two types of all-polymer lasers; (1) a Distributed FeedBack (DFB) and (2) a Distributed Bragg Reflector (DBR) laser. DFB lasers are made of alternating layers of undoped and dye-doped polymers and folded to create a spectral defect in the center of the reflection band.…”