Method for characterizing an optoelectronic device and associated characterization device

Abstract

The present invention relates to a method for characterizing an optoelectronic device (10) capable of emitting an electromagnetic beam in an operating wavelength band, the method comprising the following steps: - the optoelectronic device (10) emitting an electromagnetic beam; - a detection unit (20) carrying out a series of measurements on a portion of the electromagnetic beam emitted in a secondary wavelength band included in the operating wavelength band and excluding the main wavelength band; and - a processing unit (22) determining characteristics of the optoelectronic device (10) according to the series of measurements carried out, at least one characteristic being obtained for a secondary wavelength band, the determined characteristics allowing the operation of the optoelectronic device (10) to be assessed.

Description

[0001] DESCRIPTION

[0002] TITLE: Method for characterizing an optoelectronic device and associated characterization device

[0003] The present invention relates to a method for characterizing at least one optoelectronic device. The present invention also relates to an associated characterization device.

[0004] Optoelectronic devices are devices that emit light and interact with it, such as lasers, laser diodes, photodetectors or modulators.

[0005] Such optoelectronic devices are routinely characterized. Characterization aims to determine specific characteristics of these devices. This characterization is particularly useful for selection, diagnostics, performance or robustness evaluation, and monitoring.

[0006] However, some optoelectronic devices, and in particular GaAs (gallium arsenide) based lasers, are subject to sudden catastrophic degradations (both inside the "bulk" of the device and outside), and current characterization methods do not allow the detection of early signs of degradation.

[0007] Therefore, there is a need for a characterization method to improve the detection of early degradation of optoelectronic devices.

[0008] To this end, the present description relates to a method for characterizing at least one optoelectronic device in order to detect early degradations of said optoelectronic device, the optoelectronic device being capable of emitting an electromagnetic beam in a band of operating wavelengths, the electromagnetic beam having an emission peak for which the quantity of energy of the electromagnetic beam is the highest, the emission peak extending over a band of main wavelengths, the wavelengths outside the main wavelength band being called secondary wavelengths, the method comprising the following steps: emission of at least one electromagnetic beam by the optoelectronic device under predetermined current and temperature conditions, performance, by a detection unit, of at least one series of measurements on the emitted electromagnetic beam(s),whereby at least one series of measurements is carried out on a portion of the electromagnetic beam emitted in at least one secondary wavelength band, each secondary wavelength band being included within the operating wavelength band and excluding the primary wavelength band, each series of measurements relating to the evolution of a first quantity as a function of a second quantity, and a processing unit determines the characteristics of the optoelectronic device as a function of the series of measurements carried out, at least one characteristic being obtained for a secondary wavelength band in order to detect early degradations of said optoelectronic device, the determined characteristics allowing the operation of the optoelectronic device to be evaluated.

[0009] Depending on specific embodiments, the process comprises one or more of the following characteristics, taken individually or in all technically possible combinations:

[0010] - the first quantity is the power and the second quantity is the current intensity across the terminals of the optoelectronic device, at least one determined characteristic being a current-power characteristic in a band of secondary wavelengths;

[0011] - the process further includes an accelerated aging step of the optoelectronic device by increasing, over a predetermined period, the current intensity across the terminals of the optoelectronic device and / or the temperature, beyond the operating limits of the optoelectronic device, the emission, realization and determination steps then being repeated for the aged optoelectronic device, the process also including a step of evaluating the stability of the optoelectronic device by comparing the variations between the current-power characteristics obtained before and after the accelerated aging;

[0012] - the process further includes the steps of: determining the variations between a current-power characteristic determined for a band of secondary wavelengths and a reference current-power characteristic for the band of secondary wavelengths, and evaluating the operating state of the optoelectronic device as a function of the variations between the current-power characteristic determined for the band of secondary wavelengths and the reference current-power characteristic for the band of secondary wavelengths;

[0013] - the optoelectronic device is a device conditioned during use, the reference current-power characteristic for the secondary wavelength band having been obtained on the optoelectronic device before its conditioning or before its commissioning;

[0014] - the optoelectronic device belongs to a series of optoelectronic devices of the same nature, the emission step being implemented for a current intensity and / or for a temperature beyond the operating limits of the optoelectronic device, the first quantity being the power and the second quantity being the time, at least one determined characteristic being a time-power characteristic in a band of secondary wavelengths, the process comprising the repetition of the emission, realization and determination steps for a set of N optoelectronic devices of the series, N being an integer greater than or equal to 10, the time-power characteristics determined for the set of N optoelectronic devices allowing the aging of the N optoelectronic devices of the series to be characterized;

[0015] - the process further includes a step of constructing, by the processing unit, a statistical model of time-power characteristics in the secondary wavelength band for the series of optoelectronic devices, as a function of the time-power characteristics determined in the secondary wavelength band for the set of N optoelectronic devices, the statistical model obtained making it possible to characterize the aging of the series of optoelectronic devices,

[0016] - the process advantageously comprising the steps of: determining an average lifetime or a median lifetime for the series of optoelectronic devices as a function of the statistical model,

[0017] - sorting of the series of optoelectronic devices consisting of keeping the series of optoelectronic devices when the average lifetime or median lifetime is greater than or equal to a reference lifetime, and eliminating the series of optoelectronic devices otherwise;

[0018] - the process includes determining the power variations of each optoelectronic device in the series on their respective time-power characteristic, and evaluating the aging of said optoelectronic device by comparing the determined power variations to a reference power variation, the process advantageously including the individual sorting of each optoelectronic device in the series consisting of keeping each optoelectronic device when the power variations of said optoelectronic device on its time-power characteristic are below the reference power variation, and eliminating said optoelectronic device otherwise;

[0019] - during the implementation stage, at least two sets of measurements are carried out on portions of the electromagnetic beam, emitted in different directions;

[0020] - During the implementation stage, several series of measurements are carried out on portions of the electromagnetic beam, emitted in different secondary wavelength bands.

[0021] The invention also relates to a device for characterizing at least one optoelectronic device in order to detect early degradations of said optoelectronic device, the optoelectronic device being adapted to emit an electromagnetic beam in a band of operating wavelengths, the electromagnetic beam having an emission peak for which the amount of energy of the electromagnetic beam is highest, the emission peak extending over a band of main wavelengths, the wavelengths outside the main wavelength band being called secondary wavelengths, the characterization device comprising: a detection unit configured to perform at least one series of measurements on at least one electromagnetic beam emitted by the optoelectronic device,where at least one series of measurements is performed on a portion of the electromagnetic beam emitted in at least one secondary wavelength band, the secondary wavelength band being included within the operating wavelength band and excluding the primary wavelength band, each series of measurements being relative to the evolution of a first quantity as a function of a second quantity, and a processing unit configured to determine characteristics of the optoelectronic device as a function of the series of measurements performed in order to detect early degradations of said optoelectronic device, at least one characteristic being obtained for a secondary wavelength band.

[0022] Depending on specific embodiments, the characterization device comprises one or more of the following characteristics, taken individually or in all technically possible combinations:

[0023] - the detection unit includes: a beam splitter set to divide the electromagnetic beam emitted by the optoelectronic device into several sub-beams, a filtering set including one or more spectral filters, the spectral filter or filters each spectral filtering the main wavelength band and being centered on a secondary wavelength, the spectral filter or filters being positioned on the path of a sub-beam, and a detection set including detectors positioned so as to detect each sub-beam;

[0024] - the detection unit includes at least one spectrally selective photodiode so as to detect only a portion of the electromagnetic beam emitted in a band of secondary wavelengths;

[0025] - the optoelectronic device includes at least one epitaxial stack comprising at least one specific layer, the specific layer or each specific layer being capable of emitting an electromagnetic beam at a secondary wavelength (Xs), the detection unit being integrated into the optoelectronic device and configured to detect the electromagnetic beam emitted by the specific layer or each specific layer.

[0026] Other features and advantages of the invention will become apparent from the following description of embodiments of the invention, given by way of example only and with reference to the drawings which are:

[0027] - [Fig 1] Figure 1, a schematic view of an example of a characterization device,

[0028] - [Fig 2] Figure 2, a schematic view of an example of a detection unit of a characterization device,

[0029] - [Fig 3] Figure 3, a schematic view of an example embodiment of the detection unit of Figure 2,

[0030] - [Fig 4] Figure 4, a schematic view of another example embodiment of the detection unit of Figure 2,

[0031] - [Fig 5] Figure 5, a schematic view of yet another example of an embodiment of the detection unit of Figure 2,

[0032] - [Fig 6] Figure 6, a schematic view of yet another example of an embodiment of the detection unit of Figure 2,

[0033] - [Fig 7] Figure 7, a schematic view of an example of a flowchart of a process for characterizing at least one optoelectronic device,

[0034] - [Fig 8] Figure 8, an example of a graphical representation of power as a function of current over the operating wavelength band of the optoelectronic device on the one hand, and over a band of secondary wavelengths on the other hand, and

[0035] - [Fig 9] Figure 9, an example of a graphical representation of the relative variations in intensity as a function of time on the operating wavelength band of the optoelectronic device on the one hand, and on a band of secondary wavelengths on the other hand.

[0036] An example of an optoelectronic device 10 and a characterization device 12 of the optoelectronic device 10 is illustrated by Figure 1.

[0037] The optoelectronic device 10 is designed to emit an electromagnetic beam in a low-frequency (LF) operating wavelength band. The LF operating wavelength band is, for example, in the visible and / or infrared range.

[0038] The electromagnetic beam has an emission peak at which the beam energy is highest. This emission peak extends over a main wavelength band (BP) within the operating wavelength band (BF). Specifically, the main wavelength band (BP) is centered on a wavelength, called the main wavelength (XP), and its boundaries are defined by the width of the emission peak. For example, the main wavelength band (BP) extends ±3 nm around the main wavelength (i.e., an emission width of 6 nm). The main wavelength (XP) is, for example, specified by the manufacturer.

[0039] Wavelengths outside the main wavelength band BP are called secondary wavelengths Xs.

[0040] In a specific embodiment, the optoelectronic device 10 consists of one or more quantum wells delimited by barriers. In this configuration, the quantum well(s) emit the portion of the electromagnetic beam in the main wavelength band, and the barriers emit the portion of the electromagnetic beam in the secondary wavelengths.

[0041] For example, the optoelectronic device 10 is a laser, a laser diode, a photodetector or a modulator.

[0042] The characterization device 12 is suitable for determining specific characteristics of the optoelectronic device 10, allowing it to be characterized, for example during its design, or during its operation.

[0043] In particular, the characterization device 12 is designed to determine one or more characteristics in at least one secondary wavelength band BS. Each secondary wavelength band BS is included within the operating wavelength band BF and excludes the primary wavelength band BP. This allows for the detection of variations in certain quantities that would otherwise be masked by the portion of the beam within the primary wavelength band BP. These variations thus improve the detection of early degradations in the optoelectronic device 10.

[0044] In one embodiment, the characterization device 12 is integrated into an aging chamber (also called an aging bay). The aging chamber presents controllable current and temperature conditions, in particular beyond the operating limits of the optoelectronic device, so as to accelerate the aging of the optoelectronic device.

[0045] As illustrated by Figure 1, the characterization device 12 comprises a detection unit 20 and a processing unit 22.

[0046] The detection unit 20 is configured to perform at least one series of measurements on a portion of the emitted electromagnetic beam in at least one secondary wavelength band BS. The secondary wavelength band(s) BS is included in the operating wavelength band BF and excludes the primary wavelength band BP.

[0047] For example, the optoelectronic device 10 includes a fiber output. The portion of the electromagnetic beam emitted in at least one secondary wavelength band BS is, for example, sampled from the fiber output (e.g., 1% sampled). The sampling is, for example, carried out via another fiber. In another example, the portion of the electromagnetic beam emitted in at least one secondary wavelength band BS is, for example, isolated from the main beam via an optical element, such as a Bragg grating.

[0048] Each series of measurements relates to the evolution of a first quantity as a function of a second quantity. As will be described later, the first quantity is, for example, power, and the second quantity is, for example, the current intensity across the terminals of the optoelectronic device 10 or time.

[0049] In one example of implementation, the detection unit 20 is integrated into the optoelectronic device 10 or into the packaging of the optoelectronic device 10. Alternatively, the detection unit 20 is outside the optoelectronic device 10.

[0050] Different embodiments of the detection unit 20 are given below.

[0051] In a first embodiment, as illustrated in Figures 2 and 3, the detection unit 20 comprises a beam splitter assembly 30, a filtering assembly 32, and a detection assembly 34. The beam splitter assembly 30 is designed to divide the electromagnetic beam emitted by the optoelectronic device 10 into several sub-beams. The beam splitter may or may not be polarized (or, in other words, may or may not be polarization-resolved).

[0052] The beam splitter assembly 30 includes one or more beam splitters.

[0053] Each beam splitter is chosen from a range of polarizing and non-polarizing beam splitters. A polarizing beam splitter is designed to divide light into S-polarized beams (polarization perpendicular to the plane of incidence) and P-polarized beams (polarization parallel to the plane of incidence). A non-polarizing beam splitter is designed to divide light into a specific reflection / transmission (R / T) ratio while maintaining the initial polarization state of the incident light. For example, in the case of a 50 / 50 non-polarizing beam splitter, the transmitted P and S polarization states and the reflected P and S polarization states are divided according to the design ratio.

[0054] For example, each beam splitter is chosen from a beam splitter cube and a beam splitter blade.

[0055] In the example illustrated by Figure 3, the beam splitter assembly 30 comprises two polarizing beam splitters 40, 42. A first polarizing beam splitter 40 (cube) separates the incident electromagnetic beam Fl emitted by the optoelectronic device 10 (and after possible passage through a collimator 43) into a first sub-beam F1 polarized S and a second sub-beam F2 polarized P. A second polarizing beam splitter 42 (cube) separates the second sub-beam F2 polarized P into a third sub-beam F3 polarized P and a fourth sub-beam F4 polarized S (resulting from possible residual S polarization in the second sub-beam F2).

[0056] This principle can be generalized to many other sub-beam branches with different polarizations and specific spectral filtering, simply by using more beam splitters.

[0057] The filtering assembly 32 includes, for example, one or more spectral filters. A spectral filter is a filter specifically designed to filter an optical beam according to its wavelength.

[0058] Each spectral filter is positioned along the path of a subbeam generated by the beam splitter. Specifically, multiple spectral filters can be positioned along the path of the same subbeam. Alternatively, a filter wheel can be positioned along the path of a single subbeam, allowing the filtering to be tailored to the desired wavelength band.

[0059] The spectral filter or filters are designed to filter the main wavelength band BP and are centered on a secondary wavelength Xs, so as to allow only a portion of the corresponding subbeam to pass through in a secondary wavelength band BS.

[0060] Each spectral filter is, for example, a high-pass, low-pass, or band-stop filter to select a specific band of wavelengths.

[0061] In the example illustrated by Figure 3, three spectral filters 45, 46, 47 are positioned on the path of the third sub-beam F3, and three other spectral filters 48, 49, 50 are positioned on the path of the fourth sub-beam F4.

[0062] The detection assembly 34 includes detectors positioned to detect each sub-beam, after their possible passage through the filtering assembly 32.

[0063] Each detector is, for example, a photodiode.

[0064] In the example illustrated by Figure 3, the detection assembly 34 includes a detector 51 suitable for detecting the first sub-beam F1, a detector 52 suitable for detecting the third sub-beam F3, and a detector 53 suitable for detecting the fourth sub-beam F4.

[0065] In a second embodiment, as illustrated in Figures 4 to 6, the detection unit 20 comprises at least one spectrally selective photodiode so as to detect only a portion of the electromagnetic beam emitted in a secondary wavelength band BS. Thus, in this embodiment, each spectrally selective photodiode is adapted for a specific wavelength band and does not react to the signal in the primary wavelength band BP of the optoelectronic device 10. The spectrally selective photodiode(s) is / are also sensitive, so as to detect weak signals.

[0066] The spectrally selective photodiode(s) is preferably integrated into the optoelectronic device 10, in its assembly as delivered to the end customer.

[0067] Alternatively, the spectrally selective photodiode(s) is located outside the optoelectronic device 10 (externalized monitoring), in a subsystem incorporating the optoelectronic device 10. In this case, the spectrally selective photodiode(s) receives, for example, the portion of the electromagnetic beam via a dedicated optical fiber. For example, the subsystem is an Erbium Doped Fiber Amplifier (EDFA), and the optoelectronic device 10 is a pumping module for this amplifier. For example, using a GaAs photodiode for an InGaAs diode laser reduces the spectral detection range to 870 nm and shorter wavelengths, for a main emission at 900 nm or longer wavelengths, so that only the high-energy secondary portion of the diode laser emission is detected.

[0068] Figures 4 and 5 illustrate examples of photodiodes suitable for detecting a portion of the electromagnetic beam emitted by the optoelectronic device 10 in a band of secondary wavelengths BS, which may or may not be distinct from each other. In particular, in these examples, an optoelectronic device 10 emits an electromagnetic flux in two opposite directions (emission on the front and rear faces). In Figures 4 and 5, two photodiodes 60, 61 are positioned to receive the flux emitted in each direction. In Figure 5, an additional photodiode 62 is further positioned on one side of the optoelectronic device 10 to detect any lateral flux.In Figure 6, a photodiode 64 is positioned along one emission direction, and a collimation unit 65 (lens) followed by a separating element 66 (blade or cube) are positioned along the other emission direction, allowing the initial flux to be divided into two sub-fluxes, each sent to a respective photodiode 67, 68.

[0069] More generally, the spectrally selective photodiode or photodiodes is suitable for being positioned relative to the electromagnetic device 10 in any position enabling the detection of an electromagnetic flux, i.e. on the front face, on the back face, laterally, above or below the optoelectronic device 10.

[0070] In a third embodiment, the optoelectronic device 10 comprises an epitaxial stack including at least one specific layer. The specific layer is designed to emit an electromagnetic beam at a secondary wavelength Xs. The detection unit 20 is integrated into the optoelectronic device 10 and is configured to detect the electromagnetic beam emitted by the specific layer or layers. The detection unit 20 is, for example, a spectrally selective photodiode such that it detects only the electromagnetic beam emitted at the specific wavelength.

[0071] In one example implementation, the epitaxial stack comprises several specific layers, each capable of emitting an electromagnetic beam at a secondary wavelength λ s different. The detection unit 20 is specifically designed to detect each of the beams at secondary wavelengths  sdifferent, for example by means of several photodiodes.

[0072] It is emphasized that the first, second, and third embodiments of the detection unit 20 are suitable for combination (in all application contexts). For example, such a combination allows the collection of different monitoring signals at specific locations within the diode laser emission. These specific locations include, for example, front-facing emission using the uncoupled portion of the diode laser, lateral front-facing emission, lateral emission in the middle or rear of the diode laser, rear-facing emission with one or more diodes, or emission from the top or bottom of the component. Examples are described in Figures 4 to 6 for photodiodes, but these can be generalized to other types of detection units.

[0073] The processing unit 22 is configured to determine characteristics of the optoelectronic device 10 based on the series or series of measurements performed. At least one characteristic relates to a secondary wavelength band BS, that is, a band of wavelengths included within the operating wavelength band BF, and excluding the primary wavelength band BP.

[0074] Processing unit 22 is, for example, a calculator.

[0075] In one example implementation, the calculator interacts with a computer program product.

[0076] The computer includes, for example, a processor comprising a data processing unit, memory, and a data storage device. The computer also includes a human-machine interface, such as a screen and a display.

[0077] The computer program product includes an information storage medium.

[0078] The information storage medium is a medium readable by the computer, usually by the data processing unit. The readable information storage medium is a medium suitable for storing electronic instructions and capable of being connected to a bus of a computer system.

[0079] For example, the information storage medium is a USB key, a floppy disk or flexible disk (from the English name "Floppy disc"), an optical disc, a CD-ROM, a magneto-optical disc, a ROM memory, a RAM memory, an EPROM memory, an EEPROM memory, a magnetic card or an optical card.

[0080] The computer program containing program instructions is stored on the information storage medium.

[0081] The computer program can be loaded onto the data processing unit and is adapted to trigger the implementation of steps in a characterization process for at least one optoelectronic device 10 when the computer program is run on the processing unit of the computer. Such a characterization process will be described later. Alternatively, the processing unit 22 is an integrated circuit, for example an ASIC (Application-Specific Integrated Circuit), or a printed circuit board, for example an FPGA (Field-Programmable Gate Array).

[0082] Alternatively, processing unit 22 is a measuring device, such as an ammeter, or an optical or electrical multimeter.

[0083] A method for characterizing at least one optoelectronic device 10 using the characterization device 12 will now be described. Reference will be made to the flowchart in Figure 7 and the graphical representations in Figures 8 and 9.

[0084] General description of the process

[0085] The term "characterization" means obtaining characteristics relating to an optoelectronic device 10. This term thus covers: obtaining current-power characteristics for an optoelectronic device 10 (first mode of operation), obtaining the current operating state of an optoelectronic device 10 in operation (second mode of operation), and obtaining the aging / lifetime / power variations of an optoelectronic device 10 or a series of optoelectronic devices (third embodiment).

[0086] The characterization process includes a step 100 emission of an electromagnetic beam by the optoelectronic device 10 under predetermined current and temperature conditions.

[0087] In particular, the current conditions relate to the current intensity across the terminals of the optoelectronic device 10. The intensity is, for example, fixed according to intensity limits set by the manufacturer of the optoelectronic device 10.

[0088] Temperature conditions refer to the temperature of the environment in which the optoelectronic device 10 is located. The temperature is, for example, fixed according to temperature limits set by the manufacturer of the optoelectronic device 10 or chosen so as to intentionally accelerate the aging of the optoelectronic device 10 or to subject it to a more demanding operating state than its usual conditions of use.

[0089] The characterization process includes a step 110 of carrying out, by the detection unit 20, at least one series of measurements on the emitted electromagnetic beam.

[0090] The or at least a series of measurements is carried out on a portion of the electromagnetic beam emitted in at least one secondary wavelength band BS, i.e. a wavelength band which is included in the operating wavelength band BF and which excludes the main wavelength band BP.

[0091] Each series of measurements relates to the evolution of a first quantity as a function of a second quantity.

[0092] Preferably, during implementation step 110, at least two sets of measurements are performed on portions of the electromagnetic beam emitted in different directions. This allows for obtaining different sets of measurements, making it possible, for example, to locally characterize the state of the optoelectronic device 10.

[0093] Preferably, during implementation step 110, several series of measurements are performed on portions of the electromagnetic beam emitted in different secondary wavelength bands (BS). This allows for obtaining different series of measurements, enabling characterization across different spectral bands.

[0094] Preferably, during the implementation stage, at least one additional series of measurements is also performed concerning the evolution of a first quantity as a function of a second quantity. Each series of additional measurements is performed on the electromagnetic beam emitted in the operating wavelength band BF, that is, on the entire emitted electromagnetic beam. Thus, unlike measurements performed on the secondary wavelength band BS, the additional measurements make it possible to obtain integrated characteristics over the entire emission spectrum of the optoelectronic device 10.

[0095] The characterization process includes a step 120 in which the processing unit 22 determines the characteristics of the optoelectronic device 10 based on the series or series of measurements performed. At least one characteristic is obtained for a band of secondary wavelengths BS. The determined characteristics allow for the evaluation of the operation of the optoelectronic device 10.

[0096] The characteristics obtained for the optoelectronic device 10 then allow it to be sorted, for example by comparing it to a reference. Sorting allows the optoelectronic device 10 to be assigned to a category of devices. The categories are, for example, those grouping devices with similar characteristics, or those marking the optoelectronic device 10 as valid or invalid. This applies to the three embodiments described below.

[0097] Specific description of the process for a first embodiment: obtaining characteristics specific to the optoelectronic device

[0098] In the first embodiment, the first quantity is the power and the second quantity is the current intensity across the terminals of the optoelectronic device 10. At least one determined characteristic is a current-power characteristic in a secondary wavelength band BS. The current-power characteristic in the secondary wavelength band BS potentially exhibits variations that would not have been visible in the overall incident beam, thus allowing for a more detailed characterization of the optoelectronic device 10.

[0099] This is particularly visible in the example of figure 8 for which the optoelectronic device 10 is an InGaAs laser diode and the detection unit 20 is a GaAs photodiode (cutoff wavelength at approximately 870nm, for low-pass filtering).

[0100] The thin line represents the current-power characteristic over a secondary wavelength band BS (filtered signal, here a wavelength band below 850 nm). The bold line represents the current-power characteristic over the operating wavelength band LF (integrated signal), also known as the general current-power characteristic. It is evident that the current-power characteristic over the secondary wavelength band BS exhibits power variations that are not visible on the current-power characteristic over the operating wavelength band LF. In particular, the weak filtered signal will show the initial evolution of the device relative to the integrated signal, for which slight variations are generally included in the measurement error and cannot be considered significant as a tracer of device evolution.These power variations thus allow us to better characterize the optoelectronic device 10, for example, its aging.

[0101] Optionally, the process further includes a step 200 of accelerated aging of the optoelectronic device 10 by increasing, over a predetermined period, the intensity of the current across the terminals of the optoelectronic device 10 and / or the temperature, beyond the operating limits of the optoelectronic device 10.

[0102] The emission, realization and determination steps are then repeated for the aged optoelectronic device 10.

[0103] In this case, the method also includes a step 210 for evaluating the stability of the optoelectronic device 10 by comparing the variations between the current-power characteristics obtained before and after accelerated aging. In particular, if the power variations between the two characteristics are less than a predetermined threshold, then the optoelectronic device 10 is considered stable over time. Otherwise, the optoelectronic device 10 is considered unstable over time. Specific description of the method for a second embodiment: monitoring the operation of an optoelectronic device

[0104] In the second embodiment, the optoelectronic device 10 is a functioning device. The aim of the method here is to evaluate the proper functioning of the optoelectronic device 10.

[0105] In the second embodiment, the first quantity is the power and the second quantity is the current intensity across the terminals of the optoelectronic device 10.

[0106] At least one determined characteristic is a current-power characteristic in a secondary wavelength band BS. The current-power characteristic in the secondary wavelength band BS potentially exhibits variations that would have been invisible in the overall incident beam, thus allowing for a more detailed characterization of the optoelectronic device 10.

[0107] The example in Figure 8 described for the first embodiment also applies to the second embodiment.

[0108] In the second embodiment, the method further includes a step 300 of determining the variations between a current-power characteristic determined for a secondary wavelength band BS and a reference current-power characteristic for the secondary wavelength band BS.

[0109] The process also includes a step 310 of evaluating the operating state of the optoelectronic device 10 as a function of the variations between the current-power characteristic determined for the secondary wavelength band BS and the reference current-power characteristic for the secondary wavelength band BS.

[0110] In particular, if the power variations between the two characteristics are less than a predetermined threshold, then the optoelectronic device 10 is considered to be in good working order. Otherwise, the optoelectronic device 10 is considered to be in poor working order (because it shows early signs of degradation undetectable on the main signal), which allows for maintenance or replacement of the optoelectronic device 10.

[0111] For example, in this second embodiment, the optoelectronic device 10 is a device conditioned during use. The reference current-power characteristic was, for example, obtained on the optoelectronic device 10 before its conditioning or before its commissioning, for example using a characterization process as described for the first embodiment. Specific description of the process for a third embodiment: determination of an aging model for a series of optoelectronic devices

[0112] In this third embodiment, the optoelectronic device 10 belongs to a series of optoelectronic devices of the same type. The aim of the process in this case is to sort the series of optoelectronic devices (by series or individually within the same series).

[0113] The emission step is implemented for a current intensity and / or for a temperature beyond the operating limits of the optoelectronic device 10. This allows premature aging of the optoelectronic device 10.

[0114] The first quantity is power and the second quantity is time.

[0115] At least one determined characteristic is a time-power characteristic in a secondary wavelength band BS.

[0116] Figure 9 illustrates an example of a time-power characteristic over a secondary wavelength band BS (here, a wavelength band below 850 nm, filtered signal) on the one hand, and over an operating wavelength band BF on the other (integrated signal). Figure 9 shows an increase in the relative variation of the signal for the filtered signal (6% increase) compared to the integrated signal (1% decrease).

[0117] In the case of Figure 9, spectral filtering was also carried out using low-pass filters with 50 nm steps, and therefore the filter closest to a GaAs photodiode is the 850 nm filter.

[0118] Alternatively, the use of high-pass filters in the SWIR (near-infrared) region allows for increased sensitivity in detecting "gap" signals from the active region of the diode laser or the active region of the InGaAs diode laser, often associated with defects in the semiconductor material.

[0119] The process includes repeating the emission, realization, and determination steps for a set of N optoelectronic devices in the series. N is an integer greater than or equal to 10.

[0120] The time-power characteristics determined for the set of N optoelectronic devices allow the aging of the N optoelectronic devices in the series to be characterized.

[0121] In a first example, the process further includes a step 400 in which the processing unit 22 constructs a statistical model of time-power characteristics for the series of optoelectronic devices based on the time-power characteristics determined for the set of N optoelectronic devices. The resulting statistical model allows the aging of the series of optoelectronic devices to be characterized.

[0122] Optionally, the process also includes a step 410 of determining an average lifetime or median lifetime for the series of optoelectronic devices based on the statistical model.

[0123] Optionally, the process also includes sorting the series of optoelectronic devices by keeping the series of optoelectronic devices when the mean lifetime or median lifetime is greater than or equal to a reference lifetime, and eliminating the series of optoelectronic devices otherwise.

[0124] In a second example, the process includes determining the power variations of each optoelectronic device in the series on their respective time-power characteristic, and evaluating the aging of said optoelectronic device by comparing the determined power variations to a reference power variation.

[0125] The reference power variation is, for example, determined based on the power variations of the N optoelectronic devices in the series. The reference power variation is, for example, the mean or median of the power variations of the N optoelectronic devices in the series.

[0126] Alternatively, the reference power variation is a predetermined value, for example set at 0.5%.

[0127] Optionally, the process also includes the individual sorting (burn-in) of each optoelectronic device in the series, consisting of keeping each optoelectronic device when the power variations of said optoelectronic device on its time-power characteristic are below the reference power variation, and eliminating said optoelectronic device otherwise.

[0128] Thus, the present method makes it possible to provide more information on the characterized device, and, in particular, this additional information is more sensitive to the evolution of the device itself, which will also allow for more effective screening of populations and for obtaining detailed information on the optoelectronic device 10 itself, thus providing means for more effective screening of populations and for detailed characterization of a single device.

[0129] In particular, the present method makes it possible to increase the sensitivity of monitoring the operation of an optoelectronic device, regardless of the objective of this monitoring, whether it be better control of its lifespan, screening for specific devices with potential weaknesses, or any other monitoring objective. Furthermore, such a method makes it possible to cover a higher dynamic range (in terms of detected light intensity) than prior art spectrum analyzers. Indeed, the detector(s) of the detection unit can have a wide dynamic range. Moreover, with multiple detectors, this dynamic range is even higher.

[0130] Those skilled in the art will understand that the embodiments described above can be combined when such combinations are compatible. Furthermore, the invention also extends to the following embodiments.

[0131] In preferred embodiments, the or each secondary wavelength band BS is defined with respect to the main wavelength Xp. In particular, when the main wavelength band BP extends over ± N nm (with N a positive integer) around the main wavelength XP (i.e. an emission width of 2xN nm), each secondary wavelength band BS considered is located at a distance of at least N+M nm from the main wavelength XP, with M an integer greater than or equal to 5 nm, preferably greater than or equal to 10 nm, advantageously greater than or equal to 25 nm.

[0132] Thus, as a non-limiting example, for a primary wavelength P = 900 nm, a secondary band can be selected within a window centered at XP - (N+M) = 900 - (N+M) nm (high-energy side) or XP + (N+M) = 900 + (N+M) nm (low-energy side), with a suitable selection width (e.g., on the order of a few nanometers), while excluding the primary BP band. For example, if N = 3 nm and M = 25 nm, secondary bands can be centered around 872 nm (high-energy side) and 928 nm (low-energy side). This explicit definition allows measurements to be performed in spectral regions sufficiently far from the emission peak to increase sensitivity to early degradation of the optoelectronic device.10

[0133] In preferred embodiments, the optoelectronic device 10 is a side-emitting laser, such as, for example, an InGaAs / GaAs semiconductor laser, comprising a waveguide and end mirrors (facets) defining the cavity. This preference reflects the fact that the main emission occurs via the side facets, while components at secondary wavelengths (outside the main wavelength band) may originate from peripheral regions, barriers, or material defects, and prove particularly informative for detecting early degradation. The described embodiments remain applicable to other optoelectronic devices (laser diodes, modulators, photodetectors), including surface-emitting ones, but implementation on side-emitting lasers is preferred.Preferably, the detection unit 20 performs series of measurements in secondary wavelength bands BS located both on the side of wavelengths shorter than the main wavelength Â. P (high energy side) than on the side of wavelengths greater than  P(low-energy side). This dual investigation allows for the capture of distinct signatures of the evolution of the optoelectronic device 10, with some degradations manifesting primarily at high energy, while others appear at low energy. The determined characteristics (e.g., current-power or time-power) are thus obtained separately for secondary bands below and above the main wavelength P, and compared to references to assess the state and stability of the device. Alternatively, the series of measurements performed by the detection unit 20 are carried out only on the high-energy side or only on the low-energy side.

[0134] Preferably, the present invention does not employ spatial emission profiling analysis (near-field or far-field) for the characterization of the device 10. The measurements implemented in the invention relate to measured quantities (e.g., detected optical power) in secondary wavelength bands BS excluding the main band BP, and are structured as series (evolution of a first quantity as a function of a second quantity, such as power as a function of current, or power as a function of time). The characterization criteria are derived from these characteristics obtained in the secondary bands (by comparison to references, before / after aging, or on a series of devices), without resorting to imaging metrics of a spatial emission profile.This exclusion reinforces the technical positioning on a confined characterization outside the main wavelength band BP, targeted for the detection of early degradations.

Claims

DEMANDS 1. A method for characterizing at least one optoelectronic device (10) for the purpose of detecting early degradation of said optoelectronic device (10), the optoelectronic device (10) being capable of emitting an electromagnetic beam in a band of operating wavelengths (BF), the electromagnetic beam having an emission peak for which the amount of energy of the electromagnetic beam is highest, the emission peak extending over a band of main wavelengths (BP), the wavelengths outside the band of main wavelengths (BP) being called secondary wavelengths (Xs), the method comprising the following steps: emission of at least one electromagnetic beam by the optoelectronic device (10) under predetermined current and temperature conditions, performance, by a detection unit (20), of at least one series of measurements on the or at least one emitted electromagnetic beam,whereby at least one series of measurements is carried out on a portion of the electromagnetic beam emitted in at least one secondary wavelength band (SB), each secondary wavelength band (SB) being included in the operating wavelength band (OB) and excluding the primary wavelength band (PW), each series of measurements being related to the evolution of a first quantity as a function of a second quantity, and determination, by a processing unit (22), of characteristics of the optoelectronic device (10) as a function of the series(s) of measurements carried out, at least one characteristic being obtained for a secondary wavelength band (SB) in order to detect early degradations of said optoelectronic device (10), the determined characteristics allowing the operation of the optoelectronic device (10) to be evaluated.

2. Method according to claim 1, wherein the first quantity is the power and the second quantity is the current intensity across the terminals of the optoelectronic device (10), at least one determined characteristic being a current-power characteristic in a band of secondary wavelengths (BS).

3. A method according to claim 2, wherein the method further comprises an accelerated aging step of the optoelectronic device (10) by increasing, over a predetermined period, the current intensity across the device. optoelectronic (10) and / or temperature, beyond the operating limits of the optoelectronic device (10), the emission, realization and determination steps being then repeated for the aged optoelectronic device (10), the process also including a step of evaluating the stability of the optoelectronic device (10) by comparing the variations between the current-power characteristics obtained before and after accelerated aging.

4. Method according to claim 2, wherein the method further comprises the steps of: determining the variations between a determined current-power characteristic for a secondary wavelength band (BS) and a reference current-power characteristic for the secondary wavelength band (BS), and evaluating the operating state of the optoelectronic device (10) as a function of the variations between the determined current-power characteristic for the secondary wavelength band (BS) and the reference current-power characteristic for the secondary wavelength band (BS).

5. Method according to claim 4, wherein the optoelectronic device (10) is a device conditioned in use, the reference current-power characteristic for the secondary wavelength band (SB) having been obtained on the optoelectronic device (10) before its conditioning or before its commissioning.

6. A method according to claim 1, wherein the optoelectronic device (10) belongs to a series of optoelectronic devices of the same nature, the emission step being carried out for a current intensity and / or for a temperature beyond the operating limits of the optoelectronic device (10), the first quantity being the power and the second quantity being the time, at least one determined characteristic being a time-power characteristic in a secondary wavelength band (SWB), the method comprising the repetition of the emission, realization and determination steps for a set of N optoelectronic devices of the series, N being an integer greater than or equal to 10, the time-power characteristics determined for the set of N optoelectronic devices allowing the aging of the N optoelectronic devices of the series to be characterized.

7. A method according to claim 6, wherein the method further comprises a step of constructing, by the processing unit (22), a statistical model of time-power characteristics in the secondary wavelength band (SWB) for the series of optoelectronic devices, as a function of the time-power characteristics determined in the secondary wavelength band (SWB) for the set of N optoelectronic devices, the statistical model obtained allowing the aging of the series of optoelectronic devices to be characterized, the method advantageously comprising the steps of: determining an average lifetime or a median lifetime for the series of optoelectronic devices as a function of the statistical model, - sorting of the series of optoelectronic devices consisting of keeping the series of optoelectronic devices when the average lifetime or median lifetime is greater than or equal to a reference lifetime, and eliminating the series of optoelectronic devices otherwise.

8. A method according to claim 6, wherein the method comprises determining the power variations of each optoelectronic device in the series on their respective time-power characteristic, and evaluating the aging of said optoelectronic device by comparing the determined power variations to a reference power variation, the method advantageously comprising the individual sorting of each optoelectronic device in the series consisting of keeping each optoelectronic device when the power variations of said optoelectronic device on its time-power characteristic are below the reference power variation, and eliminating said optoelectronic device otherwise.

9. A method according to any one of claims 1 to 8, wherein during the implementation step, at least two sets of measurements are carried out on portions of the electromagnetic beam, emitted in different directions.

10. A method according to any one of claims 1 to 9, wherein during the implementation step, several series of measurements are carried out on portions of the electromagnetic beam, emitted in different secondary wavelength bands (SB).

11. Characterization device (12) for at least one optoelectronic device (10) for the purpose of detecting early degradation of said optoelectronic device (10), the optoelectronic device (10) being capable of emitting an electromagnetic beam in a band of operating wavelengths (BF), the electromagnetic beam having an emission peak for which the amount of energy of the electromagnetic beam is highest, the emission peak extending over a band of main wavelengths (BP), the wavelengths outside the band of main wavelengths (BP) being called secondary wavelengths (Xs), the characterization device (12) comprising: a detection unit (20) configured to perform at least one series of measurements on at least one electromagnetic beam emitted by the optoelectronic device (10),where at least one series of measurements is carried out on a portion of the electromagnetic beam emitted in at least one secondary wavelength band (SB), the secondary wavelength band (SB) being included in the operating wavelength band (OB) and excluding the primary wavelength band (PW), each series of measurements being related to the evolution of a first quantity as a function of a second quantity, and a processing unit (22) configured to determine characteristics of the optoelectronic device (10) as a function of the series(s) of measurements carried out, at least one characteristic being obtained for a secondary wavelength band (SB) in order to detect early degradations of said optoelectronic device (10).

12. Characterization device (12) according to claim 11, wherein the detection unit (20) comprises: a beam splitter assembly (30) adapted to divide the electromagnetic beam emitted by the optoelectronic device (10) into several subbeams, a filtering assembly (32) comprising one or more spectral filters, the spectral filter or each filtering the main wavelength band (BP) and being centered on a secondary wavelength (Xs), the spectral filter or each being positioned on the path of a subbeam, and a detection assembly (34) comprising detectors positioned so as to detect each subbeam.

13. Characterization device (12) according to claim 11 or 12, wherein the detection unit (20) comprises at least one selective photodiode spectrally so as to detect only a portion of the electromagnetic beam emitted in a band of secondary wavelengths (SB).

14. Characterization device (12) according to any one of claims 11 to 13, wherein the optoelectronic device (10) comprises at least one epitaxial stack comprising at least one specific layer, the specific layer or each specific layer being capable of emitting an electromagnetic beam at a secondary wavelength (Xs), the detection unit (20) being integrated into the optoelectronic device (10) and configured to detect the electromagnetic beam emitted by the specific layer or each specific layer.

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