Thin-film filter, wavelength-locked, multi-laser cavity for dense wavelength beam combining of broad-area laser diode bars

Abstract

We report on individual wavelength locking of a multiplet of 100-μm broad-area laser diode emitters arranged on a 50% fill-factor bar by means of a single external multi-laser cavity using an ultra-narrowband thin-film filter as a dispersive optical element. The achieved wavelength-locked output power is 216 W, corresponding to an electrical-to-optical conversion efficiency of about 49.7%. The 45 emitters of the laser diode bar are stabilized within a spectral range of about 6.4 nm. Our approach is suited for killowatt-class dense wavelength beam combining of direct diode lasers.

Quasi-periodic photonic crystal Fabry–Perot optical filter based on Si/SiO2 for visible-laser spectral selectivity

“…Figure 1 shows the designed multi-layer structure of C s (Si/ SiO 2 ) 3 (SiO 2 /Si) 3 , which has been prepared on K9 optical glass (side length 2.5 cm, thickness 3 mm). The thickness of every single layer is set as follows: dH(Si) = 106.8 nm; dL(SiO 2 ) = 268.4 nm; C s = 20, 40, and 60 nm.…”

“…In order to further verify the applicability of equations ( 5) and ( 6) for our designed multi-layer structure (Si/SiO 2 ) 3 (SiO 2 / Si) 3 , we make comparisons between numerical calculation and simulation: peak transmittances T max = 1 are surprisingly consistent. FWHM by numerical calculation 3.27 (m 2 = 1, n sub = 1, λ m = 1.55 µm and x = 3) is in good agreement with the simulation value 3.2 (as shown in figure 4, by the software Essential Macleod).…”

“…In recent years, the optical filter has received much attention due to its widespread applications [1][2][3][4] in communication systems, thermophotovoltaic converters, laser diode emitters, and waveguides, which can regulate electromagnetic (EM) waves to meet various demands. Different kinds of optical filters [5][6][7], such as optical array structures, quantum dots, and thin film filters, have been investigated and designed for applying in x-ray, ultraviolet, visible light, infrared, and microwave bands [1,[7][8][9].…”

“…To realize the required colors, the surface thickness should be as thin as possible. In addition, figure 1(b) shows that the symmetrical structure (Si/SiO 2 ) 3 (SiO 2 /Si) 3 possesses a narrower FWHM than (SiO 2 /Si )3 (Si/SiO 2 ) 3 . So based on the criterion above, figure 2 specifically shows the designed structure C s (Si/SiO 2 ) 3 (SiO 2 /Si) 3 which can be expressed equivalently as C s /FPOF or C s /reflection slab A/reflection slab B, where C s represents the variable thickness surface layer of the TiO 2 (average refractive index of 2.25) [23].…”

“…In addition, figure 1(b) shows that the symmetrical structure (Si/SiO 2 ) 3 (SiO 2 /Si) 3 possesses a narrower FWHM than (SiO 2 /Si )3 (Si/SiO 2 ) 3 . So based on the criterion above, figure 2 specifically shows the designed structure C s (Si/SiO 2 ) 3 (SiO 2 /Si) 3 which can be expressed equivalently as C s /FPOF or C s /reflection slab A/reflection slab B, where C s represents the variable thickness surface layer of the TiO 2 (average refractive index of 2.25) [23]. Excellent visible-laser spectral selective performance has been achieved with a certain colored overlay and satisfactory 1.55 µm filtering characteristics.…”