1. Technical Field
The present disclosure relates to integrated optics and, particularly, to a waveguide lens.
2. Description of Related Art
Lasers are used as light sources in integrated optics as the lasers have excellent directionality, as compared to conventional light sources. However, laser beams emitted by the lasers still have a divergence angle. As such, if the laser is directly connected to an optical element, some divergent rays may not be able to enter into the optical element, decreasing light usage.
Therefore, it is desirable to provide a waveguide lens, which can overcome the above-mentioned problems.
Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure.
Embodiments of the present disclosure will be described with reference to the drawings.
Referring to
In detail, the media grating 130 includes a number of media strips 131. Each media strip 131 and the planar waveguide 120 cooperatively form a strip-loaded waveguide. An effective refractive index of portions of the planar waveguide 120 where each media strip 131 is located (i.e., a portion of the planar waveguide 120 beneath each media strip 131) is increased. As such, by properly constructing the media grating 130, for example, constructing the media grating 130 as a chirped grating, the media grating 130 and the planar waveguide 120 can function as, e.g., a chirped diffractive waveguide lens.
By virtue of the electrodes 140 and the accompanying modulating electric field E , the effective focal length of the diffractive waveguide lens can be adjusted as desired to ensure the effective convergence of the laser beam 21 into an optical element 30 at any distance from the laser light source 20.
The substrate 110 is substantially rectangular and includes a top surface 111 and a side surface 112. In this embodiment, the substrate 110 is made of lithium niobate (LiNbO3) crystal.
The planar waveguide 120 is formed by coating a film of titanium (Ti) on the top surface 111 and then diffusing the Ti into the top surface 111 by a high temperature diffusion technology. That is, the planar waveguide 120 is made of LiNbO3 diffused with Ti (Ti: LiNbO3), of which the effective refractive index gradually changes along the widthwise direction thereof, benefitting the creating of the diffractive waveguide lens. After the planar waveguide 120 is formed, the top surface 111 becomes an upper surface of the planar waveguide 120.
The media grating 130, such as a chirped grating, is formed by etching the upper surface of the planar waveguide 120 (i.e., the top surface 111). That is, the media grating 130 is also made of Ti:LiNbO3. After the media grating is formed, the top surface 111 is an upper surface of the media grating 130. There are an odd number of the media strips 131. The media strips 131 are symmetrical about a widthwise central axis OO′ of the media grating 130. Each of the media strips 131 are parallel and rectangular. In order from the widthwise central axis OO′ outwards to each side, widths of the media strips 131 decrease, and widths of gaps between each two adjacent media strips 131 also decrease.
Referring to
The boundaries of the media strips 131 where xn<0 can be determined by the characteristics of symmetry of the media grating 130.
The electrodes 140 are symmetrical about the central axis OO′ and aligned with the media grating 130 so as to be parallel to the media strips 131. A length of each of the electrodes 140 is longer or equal to a length of the media grating 130, and height of each of the electrodes 140 is greater than or equal to a height of the media grating 130. As such, the modulating electric field E can effectively modulate the light beam 21 to change the effective refractive index of the planar waveguide 120.
The laser light source 20 can be a distributed feedback laser, and is attached to a portion of the side surface 112 corresponding to the planar waveguide 120. The optical axis AA′ is aligned with the widthwise central axis OO′.
The optical element 30 can be a strip waveguide, an optical fiber, or a splitter.
It will be understood that the above particular embodiments are shown and described by way of illustration only. The principles and the features of the present disclosure may be employed in various and numerous embodiments thereof without departing from the scope of the disclosure as claimed. The above-described embodiments illustrate the possible scope of the disclosure but do not restrict the scope of the disclosure.
Number | Date | Country | Kind |
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101147898 | Dec 2012 | TW | national |