Super structure grating and tunable laser

A super structure grating apparatus, comprising:

• a first reflector;
• and
• a second reflector coupled to the first reflector, wherein the first reflector, the second reflector, or both the first reflector and the second reflector include a super structure grating configured to:
• spatially perform amplitude and phase modulation on a uniform grating using a modulation function to generate a comb reflection spectrum, wherein the modulation function corresponds to (N+1) modulation function discrete values when discretization processing is performed on the modulation function using N thresholds, wherein N is a positive integer greater than or equal to 2, wherein each of the (N+1) modulation function discrete values corresponds to one section of an optical waveguide whose refractive index is uniform or corresponds to one section of the uniform grating, wherein the uniform grating is an optical waveguide alternating between a high refractive index and a low refractive index, wherein a reflectivity of a reflection peak of the super structure grating is based on a relationship of a ratio of a length of an optical waveguide corresponding to at least one of the (N+1) modulation function discrete values to a total grating length of the super structure grating, and based on the total grating length of the super structure grating, and wherein a full width half maximum (FWHM) of the reflection peak of the super structure grating is based on the ratio and the total grating length of the super structure grating.