VCSEL Packaging Assembly with Prism Lens for Signal Loss Reduction
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Solution Overview
Problem
Conventional TO-CAN packages for vertical-cavity surface-emitting lasers (VCSELs) face issues with optical interference and longer bonding wires due to the VCSEL element being positioned under the optical axis, leading to increased signal loss and reduced transmission speed in high-speed applications.
Innovation Solution
A packaging assembly that uses a lens assembly with a half-reflecting, half-transmitting surface to split the laser beam, directing a portion to a monitor photodiode and allowing the VCSEL element to be positioned closer to the pins, thereby shortening bonding wires and reducing signal loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the VCSEL element is disposed right under the optical axis in a conventional TO-CAN package, then the laser beam can travel directly along the optical axis, but optical interference arises due to reflection from the lens or translucent plate on the cap
Solution Approach 1:
The VCSEL element is intentionally offset from the optical axis, creating an asymmetric arrangement. The lens assembly is positioned at a specific lateral distance from the optical axis, and the laser beam is directed to pass through the lens at an angled path rather than vertically. This asymmetric configuration ensures that the reflected light from the lens does not return to the VCSEL element, eliminating optical interference while maintaining efficient beam transmission.
2Device complexity
If the VCSEL element is disposed right at the center of the packaging assembly, then the structure is simplified, but the distance between the VCSEL element and the signal-transmitting pin is too long, requiring longer bonding wires and increasing signal loss
Solution Approach 1:
The design transitions from a conventional centered vertical arrangement to a lateral offset configuration. By moving the VCSEL element away from the central optical axis position and placing it closer to the signal-transmitting pin in the lateral dimension, the bonding wire length is significantly reduced. The lens assembly compensates for the offset position by being positioned at a specific lateral distance, ensuring proper beam alignment without requiring the VCSEL to be at the center.
3Loss of energy
If the VCSEL element is relocated closer to the pin, then bonding wire length is reduced and signal loss decreases, but the laser beam path must be redirected away from the optical axis
Solution Approach 1:
The lens assembly serves as an intermediary element that mediates between the offset VCSEL element and the optical axis. Positioned at a specific lateral distance from the optical axis, the lens receives the laser beam from the VCSEL and redirects it to travel along the desired path. This intermediary lens assembly enables the VCSEL to be located closer to the pin while maintaining proper optical alignment and beam direction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces signal loss and minimizes the impact of reflected light from the lens or translucent plate, enabling higher transmission speeds by positioning the VCSEL element closer to the pins and optimizing the laser beam path.
Implementation Method 1
the lens assembly has thereinside a half-reflecting half-transmitting surface, the laser beam emitted by the laser element is directed into the lens assembly so as to split into a first light beam and a second light beam by the half-reflecting half-transmitting surface
Data Source
AI summary
A packaging assembly for a high-speed vertical-cavity surface-emitting laser (VCSEL) mainly applies a lens assembly consisted of several prisms to split a laser beam emitted by a VCSEL element so as to guide a small portion of the laser beam back to a monitor photodiode (MPD) and the rest of the laser beam to travel away along an optical axis. Such a spectacular design of the lens assembly can not only relieve the VCSEL element from a position right under the optical axis, but can also reduce signal loss by shorting a length of a bonding wire for a corresponding pin through disposing the VCSEL element further close to the corresponding pin. Thereupon, a defect of lights reflected from a lens or a translucent plate on a cap can be substantially improved.