Distributed Bragg mirrors

Interference mirrors are dielectric thin film coatings where low- and high-refractive index layers alternate. The optical thickness of each of the layers is equal to quarter-wavelength QJAn). They are denoted as distributed Bragg mirrors or distributed Bragg reflectors (DBR), sometimes simply as Bragg mirrors. Other names include quarter-wave mirrors (QWM), quarterwave stacks (QWS) and highly reflective (HR) layers. 

Figure 10-12. Lcfi hand side Slruclure of a PPV microcavily. A thin film of ihe conjugated polymer is deposited on top of a highly reflective distributed Bragg refieclor (DBR). The second mirror is then fabricated by evaporation of a silver layer. Right hand side Emission spectra of the microcavily at excitation cnetgics or 0.0S pJ (dashed line) and l. l pJ (solid line), respectively. Laser pulses ol duration 200-300 ps and a wavelength of 355 nm were used for optical excitation (according to Ref. [39]).

Although many diode lasers work as multimode lasers, the distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers show a mode selection because of their periodic structure. The mode selectivity is generated by the optical properties of the periodic stmctures because (Mily the modes that are associated with a standing wave/stop band are amplified. DFB structures are photonic structures, which are doped throughout the volume with chromophores (in an optimal case at the maxima of the standing waves), whereas DBR lasers have a miniature Fabry-Perot cavity in which the dye is localized, and the mirrors are replaced by periodic gratings [85]. 

Distributed Bragg reflector Tunable, broadband PBG Tunable mirrors dichroic uv, (Zheng et al. 2004 MIAO... 

In ID case a defectless photonic crystal reduces to a Bragg distributed mirror (DBR). The defect modifies its spectral characteristics by introducing a transmission maximum dependent on the defect properties and deforms the ID photonic bands to some extent. 

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