End-Pumped VECSEL With Perpendicular Pumping
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Solution Overview
Problem
The existing vertical external cavity surface emitting lasers (VECSELs) face challenges in mass production and size reduction due to complex manufacturing processes and significant reflection losses caused by the angled incidence of the pump laser beam, which also limits the efficiency of the second harmonic generation (SHG) crystal.
Innovation Solution
An end-pumped VECSEL design where the pump laser emits light perpendicular to the laser chip, aligned with other components, allowing for a simpler manufacturing process, reduced size, and efficient heat dissipation, with a thermal conductive submount to transfer heat and pump light, and an SHG crystal positioned closer to the laser chip for increased efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the pump laser is aligned at an angle to the laser chip, then the pump laser beam can be provided to the laser chip, but the manufacturing process becomes complex and time-consuming, rendering mass-production difficult
Solution Approach 1:
Instead of aligning the pump laser at an angle to the laser chip as in conventional designs, this invention inverts the approach by making the pump laser beam incident perpendicular (at 90 degrees) to the laser chip surface. This fundamental geometric inversion simplifies the alignment process and enables mass production while maintaining effective optical pumping.
2Loss of energy
If the pump laser beam is incident on the laser chip at about 45 degrees, then the pump laser can activate the laser chip, but significant reflection loss occurs and oscillation efficiency drops
Solution Approach 1:
The invention changes the critical parameter of pump laser incidence angle from the conventional 45 degrees to 90 degrees (perpendicular incidence). This parameter change eliminates significant reflection losses that occur at angled incidence and maximizes oscillation efficiency while maintaining effective activation of the laser chip.
3Shape
If the pump laser beam is incident at an angle, then the laser chip can be activated, but the emitted light has an elliptical cross-section instead of circular
Solution Approach 1:
By inverting the pump laser incidence from angled to perpendicular, the invention restores the circular cross-section shape of the emitted light. The perpendicular incidence ensures symmetric coupling with the laser chip's active layer, producing circular beam profiles that are superior for most optical applications compared to elliptical sections.
4Loss of energy
If the SHG crystal is positioned close to the laser chip, then wavelength converting efficiency increases, but the pump laser beam cannot reach the laser chip from the front
Solution Approach 1:
The invention inverts the pump laser delivery path from side-angled incidence to perpendicular incidence through the heat sink. This allows the SHG crystal to be positioned close to the laser chip for maximum conversion efficiency, while the pump laser beam reaches the laser chip from the opposite direction through the heat sink's central opening, resolving the spatial conflict.
5Ease of manufacture
If the VECSEL structure is simplified for mass production, then manufacturing ease increases, but heat dissipation capability may be compromised
Solution Approach 1:
The heat sink is designed to perform multiple functions simultaneously: it serves as the thermal management component for dissipating heat from the laser chip, as the optical path medium for transmitting the pump laser beam (through its central opening), and as part of the structural support. This multi-functionality enables mass production with simplified assembly while maintaining effective heat dissipation.
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 design enables mass production of VECSELs with high efficiency, reduced reflection losses, and increased optical output power while maintaining a circular light cross-section, and enhances heat dissipation and wavelength conversion efficiency.
Implementation Method 1
a pump laser facing a bottom surface of the heat sink to emit pump light at a second wavelength perpendicular to the laser chip
Implementation Method 2
a distributed Bragg reflector (DBR) and an active layer stacked sequentially on a substrate... the DBR layer of the laser chip and the external mirror 13
Implementation Method 3
The light generated by the active layer is repeatedly reflected between the DBR layer of the laser chip 12 and the external mirror 13
Implementation Method 4
a heat sink coupled to a bottom surface of the laser chip package to dissipate heat generated by the laser chip
Implementation Method 5
a thermal conductive submount... the submount transfers the heat generated by the laser chip to the heat sink and transmits the pump light
Implementation Method 6
a thermal conductive and transparent submount located on a top surface of the heat sink
Implementation Method 7
a second harmonic generation (SHG) crystal 14 can be located between the laser chip 12 and the external mirror 13 to double the frequency of the light
Data Source
AI summary
There is provided an end-pumped vertical external cavity surface emitting laser (VECSEL) in which a pump laser beam is incident on a laser chip at a right angle. In the external cavity surface emitting laser, a laser chip package is provided with a laser chip emitting light at a first wavelength by optical pumping, an external mirror is spaced apart from a top surface of the laser chip package to transmit a portion of the light emitted from the laser chip to the outside and to reflect the remainder to the laser chip, a heat sink is coupled to the bottom surface of the laser chip package to discharge heat generated by the laser chip, and a pump laser faces a bottom surface of the heat sink to emit pump light at a second wavelength perpendicular to the laser chip.