Waveguide(s) (130) including at least partially buried channels) (120) within substrate(s) (100) having at least one substantially planar surface (110) are disclosed. According to some embodiments at least part of the channel (120) is located beneath at least a portion of the substrate (100). According to some embodiments the waveguide channel (120) includes a substantially transparent core (140) and optional cladding (160) extending through the channel (120). Alternately, an inner surface of the channel (120) is highly reflective. Furthermore, structures for use as waveguides (130) and/or as microchannels for fluid flow are disclosed herein. Also disclosed are production methods for such waveguides and said structures (130) and said structures, and methods of using such waveguides (130).