High contrast grating based saturable absorber for mode-locked lasers and its applications in passively mode-locked vertical-cavity surface-emitting lasers

An external cavity mode-locked vertical-cavity surface-emitting laser apparatus, comprising:

• a high-contrast grating saturable absorber (HCG-SA) having grating elements, with subwavelength dimensions of grating element width and spacing, of a material having an index of refraction at or exceeding approximately 2;
• a low index of refraction material, or materials, surrounding said grating elements;
• and
• said HCG-SA having high index of refraction cladding surrounding at least one optically absorbing layer;
• a semiconductor active structure disposed in separation from said high-contrast grating saturable absorber, wherein said separation forms part of a vertical cavity;
• an active region within said vertical cavity surface emitting laser upon which a lens effect of said HCG-SA is focused;
• and
• a bottom mirror positioned beneath said active region.

A monolithic passively mode-locked vertical cavity surface emitting laser (VCSEL) apparatus, comprising:

• a top output mirror;
• an active region of a vertical cavity surface emitting laser disposed in separation below a low refractive index material, or materials, which are proximal said top output mirror;
• a bottom mirror positioned beneath said active region and comprising a high-contrast grating saturable absorber (HCG-SA) having grating elements with subwavelength dimensions in width and/or spacing, of a material with an index of refraction at or exceeding approximately 2;
• and
• at least one optically absorbing structure layer within said HCG-SA surrounded by high index of refraction cladding;
• wherein said top mirror, bottom mirror, active layer, and low index of refraction material or materials, are fabricated into a monolithic VCSEL structure having an internal cavity.