TO-can Laser Device Optical Isolator Using Waveplate
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Solution Overview
Problem
The challenge is to implement a chirp managed laser device with an optical isolator function in a TO-can type package of subminiature diameter, which effectively prevents light feedback to the laser diode chip, while avoiding the complexity and expense of existing optical isolators that include two polarizers, a Faraday rotator, and a permanent magnet.
Innovation Solution
The solution involves a TO-can type laser device with a laser diode chip, a wavelength selective filter, a collimating lens, a 45 degree partial reflection mirror, and a λ/4 waveplate, where the 45 degree partial reflection mirror has high reflectance for S-polarized light and high transmittance for P-polarized light, and the λ/4 waveplate converts linear polarization to circular polarization, effectively interrupting light feedback by changing polarization upon reflection from the wavelength selective filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional optical isolator (with two polarizers, Faraday rotator, and permanent magnet) is used to prevent light feedback, then the optical isolator function is achieved, but the device size and cost increase significantly
Solution Approach 1:
The patent combines the optical isolator function with the existing wavelength selective filter (WSF) by adding a λ/4 waveplate. The WSF and waveplate work together to provide both wavelength selection and optical isolation, eliminating the need for separate polarizers and Faraday rotators. This merging reduces component count while maintaining the optical isolator function.
Solution Approach 2:
The wavelength selective filter is given dual functionality: it serves both as a wavelength selector and as part of the optical isolator system. By adding the λ/4 waveplate, the WSF assembly performs multiple functions (wavelength filtering and feedback prevention) that would traditionally require separate components, thereby reducing overall device complexity.
2Reliability
If a conventional optical isolator (with two polarizers, Faraday rotator, and permanent magnet) is used to prevent light feedback, then the optical isolator function is achieved, but the manufacturing cost increases
Solution Approach 1:
The patent merges the optical isolator function into the existing wavelength selective filter assembly by adding only a λ/4 waveplate. This eliminates the need to manufacture and assemble separate polarizers, Faraday rotators, and permanent magnets, significantly reducing manufacturing complexity and cost while maintaining the optical isolator function.
Solution Approach 2:
The patent extracts only the essential component needed to add optical isolation functionality to the existing WSF system—the λ/4 waveplate—rather than implementing a complete conventional optical isolator. This selective extraction minimizes additional manufacturing cost and complexity.
3Volume of moving object
If the TO-can type package diameter is reduced to subminiature size, then the device size is reduced for SFP module integration, but the space for optical components becomes extremely limited
Solution Approach 1:
The patent arranges optical components in a nested or compact layered configuration within the TO-can package. The λ/4 waveplate is positioned between the laser diode chip and the WSF, with components optimized for minimal spacing. This nested arrangement allows all necessary components to fit within the subminiature diameter while maintaining proper optical paths.
Solution Approach 2:
The patent optimizes the spatial arrangement of optical components by utilizing vertical stacking and angular positioning (45-degree mounting of WSF) rather than only horizontal placement. This dimensional optimization allows components to be arranged in three-dimensional space efficiently, fitting more functionality into the limited lateral space of the subminiature TO-can package.
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
This configuration effectively prevents light feedback to the laser diode chip, improving communication quality and reducing the size and cost of the optical isolator function, suitable for high-speed and long-distance communications in a compact TO-can type package.
Implementation Method 1
a collimating lens configured to be installed on an optical path between the laser diode chip and the wavelength selective filter to collimate the light emitted from the laser diode chip
Implementation Method 2
the 45 degree partial reflection mirror has high reflectance for S-polarized light and high transmittance for P-polarized light
Implementation Method 3
a 45 degree partial reflection mirror configured to be installed on an optical path between the collimating lens and the wavelength selective filter
Implementation Method 4
a λ/4 waveplate configured to be disposed between the 45 degree partial reflection mirror and the wavelength selective filter
Implementation Method 5
a wavelength selective filter
Data Source
AI summary
Disclosed herein is a technology of effectively interrupting light reflected from a wavelength selective filter so as not to be fed back to a laser diode chip in a semiconductor laser package having a function of adjusting a relative intensity ratio of a signal of “1” and a signal of “0” using an optical filter. Since an optical interruption device according to the present invention may effectively interrupt a light feedback to the laser diode chip by adjusting characteristics of a 45 degree partial reflection mirror in an existing TO-can type laser device having the 45 degree partial reflection mirror and additionally disposing one λ/4 waveplate, unlike an optical isolator according to the related art using an existing Faraday rotator, the signals of “1” and “0” may be effectively adjusted in a TO-can type laser device having a small volume, thereby improving a function of communication.