Patent ID: 6947641

Claim:
An apparatus for filtering optical radiation at an operating wavelength, comprising a waveguide, and wherein a grating is written into the waveguide and the grating is defined by a first end and a second end, and the grating comprises: a first reflector defined by a first refractive index profile; a second reflector defined by a second refractive index profile; a third reflector defined by a third refractive index profile; and wherein: the first end is connected to the first reflector, the first reflector is connected to the second reflector, and the second reflector is connected to the third reflector; the grating is defined by a first bandwidth, a maximum reflectivity, a first group delay variation with respect to the first bandwidth and the first end, a second group delay variation with respect to the first bandwidth and the second end, a first impulse response defined with respect to the first end, and a second impulse response defined with respect to the second end; and the first refractive index profile is proportional to a truncation of the first impulse response, the second refractive index profile is proportional to a truncation of the second impulse response, the maximum reflectivity is greater than 50%, the first group delay variation is between 0.1 ps and 100 ps, and the second group delay variation is between 0.1 ps and 100 ps.