Numerical analysis on heat transfer of laser diode module by equivalent electrical network method

Abstract

Because it is complex and inconvenient to use the common temperature field calculating method and experiment method, for analyzing heat transfer properties of laser diode module (LDM), an equivalent electrical network method is presented in this paper. Simulation results show that the temperature stability is closely related to ambient temperature, heat sink, LDM current and TEC current. Ambient temperature and TEC controller are the dominant terms effecting on temperature control in practice.Currently high-performance LDs are produced and packaged mostly as laser diode module (LDM). In order to ensure the stability and reliability of LDM, it is very important to set and maintain a stable temperature. Therefore, heat transfer analysis and thermal control of the LDM are very need.Heat generation and dissipation in LD packages without TEC have been investigated both analytically and experimentally [1][2][3][4] . However, the thermal analysis of LDM incorporated with a TEC has not yet been sufficiently investigated. The heat transfer analysis of a LDM is complicated considering the factors of conduction through the submount, natural convection to the gas, cooling characteristic of the TEC, thermal contact resistance with the package, performance of the heat sink, and so on. In addition, the material thermal property, the location of components and the pressure of the inert gas make the analysis more difficult.The finite element method to analyze a LDM has been presented in ref [5][6][7]. But the numerical method for analyzing heat transfer characteristics of LDM suffers from a great limitation. Due to the fact that TEC's performance does not obey standard rules of conduction, the solution how to add TEC in model becomes a key issue. At the same time, the method is complex because many parameters of LDM is needed. In this paper, a new equivalent electrical network method to analyze the characteristics of a LDM is presented.The LDM is divided into six lumped thermal control nodes: LD chip, chip carrier, submount, TEC, package and Fig.1 Block diagram of a typical LDMFor easy of analysing,we suppose that (a) the heat sources will be concentrated in the active region of LD chip ;(b) the thermal conductivity and heat capacity of materials maintain a constant value, with no temperature change.When the current I t f I flows through the LD, the Joule heat f generated by this current will be Q LD and its temperature will be T j T T . The heat transfer path begins from the junction, to the chip, carrier and submount to TEC top side. The rates of heat transfer from the controlled side of TEC (Q c ) and from the uncontrolled side (Q u ) may be determined by surface energy balances. As also, TEC pump heat comes from the top side at the temperature of T cs and goes to another side at the temperature of T us . Finally, all heat will pass the package resistance R pac , heat sink resistance R ha . So the following equation (1) could be obtaned: * heat sink.A typical LDM is shown in Fig.1. For the confined space of LDM under normal wo...

Dynamic thermal modeling and parameter identification for a monolithic laser diode module

“…Mitrani [19] proposed a one-dimensional distributed parameter transient model for thermoelectric devices implemented by analogies between the thermal and electrical domains, where thermal variables are described by the corresponding electrical analogues. Through an equivalent electrical network, Yang et al [20] analyzed the temperature control of the LDM by TEC, and demonstrated the steady state of the device.…”